MILD TO THE SKIN, FOAMING DETERGENT COMPOSITION TECHNICAL FIELD The present invention relates to mild to the skin, foaming aqueous detergent compositions comprising mixed surfactants and in particular to mixtures of anionic surfactant and biosurfactant. The compositions are suitable for use in personal wash, shower gel or shampoo formulations. BACKGROUND Sophorolipids are biosurfactants produced by several yeast species. In Candida bombicola, the hydrophilic moiety of the biosurfactant molecule is a disaccharide (i.e., sophorose), and the hydrophobic portion is an omega- or (omega-l )-hydroxy fatty acid attached to the sophorose via a glycosidic bond. The fatty acid chain, most commonly containing 16- and 18-carbon atoms, may be unsaturated and lactonized to the disaccharide. The disclosed potential applications of Sophorolipids include serving as environmentally friendly surfactants in oil recovery, and as active ingredient in detergent, cosmetic and lubricant formulations. Sophorolipids are also known to have antimicrobial activity. Sophorolipids produced by Torulopsis sp. consist of a dimeric sugar (sophorose) and a hydroxyl fatty acid linked by a B-glycosidic bond. There are generally considered to be two types of sophorolipids, the acidic (nonlactonic) and the lactonic sophorolipids. The hydroxyl fatty acid moiety of the acidic Sophorolipids forms a macrocyclic lactone ring with the 4"-hydroxyl group of the sophorose by intramolecular esterification. Lactonic Sophorolipids have attracted more attention then their acidic counterparts. The acetylated lactonic Sophorolipids have been applied in cosmetics as antidandruff, bacteriostatic agents and deodorants. Sophorolipids may be obtained from Candida apicola, Candida bombicola ATCC 22214, Candida lipolytica and Candida bogoriensis when grown on carbohydrates, hydrocarbons, vegetable oils or their mixtures. They are produced as a mixture of six to eight different hydrophobic sophorosides. EP 499 434 (Unilever) discloses the improved oily soil detergency of mixtures of a sophorolipid (SOL-TUBS a sophoroselipid from technical University of Braunchweig, Germany); produced by torulosis bombicola. It comprised a mixture of four different sophorolipids, the main fatty acid chain length being Cis. Examples 5, 6 and 7 of this patent application use blends of sophorolipids with specified nonionic surfactants. The nonionic cosurfactants used were: Synperonic A3 (an alcohol ethoxylate containing a certain amount of branching in the hydrophobe and manufactured from petrochemical fatty alcohol by reaction with 3 moles of ethylene oxide), a C12 ,2-diol and a C10 monoglycerolether. The application also suggests that the biosurfactants can be used with anionic surfactant: dialkyl sulphosuccinates are said to be of especial interest on page 7 . There is no mention of mildness or foaming. US 541 7879 (Unilever) also discloses combinations of glycolipid and nonglycolipid surfactants for oily / fatty soil detergency. Sophorolipids are mentioned among the glycolipids and dialkylsulphosuccinat.es are mentioned among the preferred non-glycolipid surfactants. However, all of the examples with sophorolipids use nonionic cosurfactants. US 5520839 (Unilever) makes a similar general disclosure and synergistic detergency claim, but also describes specific examples of dialkyl sulphosuccinates to include those in which both alkyl substituents contain at least 4 carbon atoms, and together contain 12 to 20 carbon atoms in total; such as di- Cs alkyl sulphosuccinate. This surfactant was exemplified with rhamnolipid, but the sophorolipids were only exemplified in combination with nonionic surfactants. DE 19600743 (Henkel) discloses combinations of sophorolipids and anionic surfactants. No disclosure of combinations with dialkoxy sulphosuccinates or alkyl glycinate is made. EP 1 445 302 (Ecover) discloses a detergent composition comprising at least one glycolipid biosurfactant and at least one non-glycolipid surfactant. In several examples, a Sophorolipid (Sopholiance from methyl ester of rapeseed oil ex Soliance) was used. Foam quality when used in combination with various nonionic surfactants and also anionic surfactant (SLS) was investigated. EP 1 953 237 (Ecover) discloses a method for producing short chain sophorolipids. It says that sophorolipids are one of the most promising biosurfactants, due to their high production yields and ease of recovery. It also says that they are mild to the skin. WO 98/1 6 192 (Alterna Inc) discloses a germicidal composition suitable for cleaning fruits, vegetables, skin and hair. The composition may comprise a mixture of anionic surfactant and sophorolipids biosurfactant. The anionic surfactants mentioned are those with biocidal activity: Sodium lauryl sulphate (SLS), Sodium lauryl ethoxy sulphate (SLES). EP 550 276 (Unilever) describes a personal care composition comprising a mild and foaming glycolipid used with a co surfactant (e.g. SLS). The glycolipid is a uronic acid derivative. No synergy is observed for either mildness or foam between the biosurfactant and the SLS or SDS. WO 96/1 2469 (Unilever) describes a personal care composition comprising a lipid, which may be a glycolipid such as a glycosyl glyceride of diacyl o dialkyl saccarides (eg a sugar ester), a surfactant and a deposition aid. Preferred mild surfactants include alkyl ether sulphate, alkyl glyceryl ether sulphate, sulphosuccinates, taurates, sarcosinates, sulphoacetates, alkyl phosphate, alkyl phosphate esters, acyl lactylate, and alkyl glutamates. Examples used SLES or APG with the sugar ester lipid. DE 196 48 439 & DE 196 00 743 (Henkel) describe the use of a mixture of glycolipids, which specifically includes sophorolipids and a long list of possible anionic surfactants, including mono and dialkyl sulphosuccinates. In the only example for each document that uses sophorolipid, it is combined with SLS as anionic surfactant. FR 2 792 193 (Lavipharm Lab) describes a cosmetic base comprising a composition rich in lipids of vegetable origin and at least one surfactant. A shampoo composition is disclosed with the lipids used in approx 1:1 ratio with a surfactant, which is itself a mixture of anionic and amphoteric surfactants. The anionic component is an alkyl sulphate. US56541 92 (Institut Francais du Petrole) discloses compositions containing an anionic and/or nonionic surfactant, and at least one glycolipid. The composition is used for decontaminating a polluted porous medium. Sulphosuccinates and sophorolipids are both mentioned. There are specific examples using combinations of sodium dioctyl sulphosuccinate and sophorolipids showing the synergistic effect on lowering of interfacial tension. Neither foaming, nor mildness to human skin is mentioned. No aqueous concentrated composition is disclosed. In use, the materials are mixed with water but there is then less than 1% of the sophorolipids. JP 2006070231 A (Saraya), discloses a biodegradable liquid cleaning composition e.g. liquid body cleaning composition for jet washing. The composition contains sophorolipids comprising 90% or more acid-type sophorolipids. The compositions are used as a liquid body cleaning composition for jet washing. The biodegradable liquid cleaning composition has excellent cleaning power and low foaming property. The acid-type sophorolipid is chemically stable in the liquid cleaning composition. KR 2004033376 A (LG Household & Healthcare Ltd) describes a cosmetics composition comprising sophorolipids. The cosmetics composition comprises, as an active ingredient, sophorolipids, which are produced from Candida bombiocola (ATCC 22214). The cosmetic composition has excellent sterilization effect as well as moisturising and softening effects on the skin. A cosmetics composition is characterized by comprising, as a biosurfactant, 0.01-1 0 weight% of sophorolipids. The composition is formulated into face lotion, nutritive emulsion, face cream and the like. WO 9534282 (INST FRANCAIS DU PETROLE) discloses cosmetic and dermatological compositions containing sophorolipid (s) - as radical scavengers, elastase inhibitors and antiinflammatory agents. There is an unmet need for a mild and high foaming surfactant system for use in personal care (cleaning) products that employs surfactant systems that can be considered relatively environmentally friendly. SUMMARY OF THE INVENTION According to the present invention there is provided a mild to the skin, foaming detergent composition comprising: a) 1 to 20 wt% sophorolipid biosurfactant, b) 1 to 20 wt% of anionic surfactant selected from the group consisting of glycinate, sulphosuccinate, and mixtures thereof, c) 0 to1 0 wt% foam boosting surfactant, d) 0 to 2 wt% additional electrolyte, e) 0 to 10 wt% additional detergent additives, f) 40 to 98 wt% water. The weight ratio a:b is preferably 3:1 to 1:3, most preferably 1.5:1 to 1:1 .5. It is preferred to select a) and b) to be both mild and foaming. However, if additional foaming is required than a foam boosting surfactant may be included as component c), the foam boosting surfactant is advantageously 2 to 8 wt% olivamidopropyl betaine, due to its mildness. The anionic surfactant component b).advantageously comprises cocoyi glycinate (sodium salt) or dialkoxy sulphosuccinate (disodium salt). The additional electrolyte component d) may comprise sodium chloride. The additional additives e) may comprise materials selected from the group: silicones, polymers, structurants thickeners, pH adjusters and mixtures thereof. The invention also comprises use of a mixture of 1-20 wt% sophorolipids and 1-20 wt% anionic surfactant selected from the group consisting of glycinate, sulphosuccinate, and mixtures thereof in a detergent composition to increase the mildness to the skin of the composition. Especially it comprises use of the composition as a mild and foaming shampoo or body wash. The invention results from the finding that a blend of a specific type of biosurfactant with a specific type of anionic surfactant shows increased mildness to skin with excellent foaming properties. Mild to the skin means: that in the skin protein protection assay described as for example 1 below the absorbance measured is greater than 0.8%. The basis of the mildness assay is the enzymatic activity of Chynnotrypsin on a chromogenic substrate. Surfactant mildness is assessed by the effect of a surfactant on the enzyme protein. A harsh surfactant will degrade Chynnotrypsin, leading to a lower optical density reading in the reaction well. The enzyme used for this assay is a- Chymotrypsin from bovine pancreas. The enzyme used is the chromogenic substrate for Chymotrypsin, N-Succinyl-Ala-Ala-Pro-Phe-pNA. The 0.8 value is for the optical density at 450nm of the system, and the units should be %, as in 0.8% of the incident light was transmitted. CHECK AGAINST EG1 etc. Foaming means: that in the foaming assay described as Phase 2 below, the foam thickness doesn't decrease significantly within 10 minutes of agitation. The inclusion of the sulphosuccinates or the glycinate reduces the amount of relatively expensive sophorolipids biosurfactant as expected but surprisingly it confers further synergistic mildness and foaming benefits as described more fully below. Blends according to the invention give both mildness and foaming. Such a combination is desired for personal products applications such as shampoo, shower gel, skin cleansing compositions, foam bath or any other cleaning composition that comes into contact with skin during its use. Thus, hand dish washing compositions, hard surface cleaning applications and some laundry composition uses could also be made using the detergent compositions of the invention. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a personal wash shower gel or shampoo formulation containing a mixture of sophorolipid and glycinate surfactants, for improved skin protein protection. Specifically the present invention comprises the use of mixture of sophorolipids, with 1 to 20 wt% of selected anionic surfactant, preferably amilite, a cocoyl glycinate (sodium salt), for improved skin protein protection. A preferred sophorolipid for such Personal Products applications, like hair shampoo, is Sopholiance S - ex Soliance. It is said to be a Candida Bombicola / Glucose / Methyl Rapeseedate Ferment (and) water (and) Potassium Sorbate. Some published analysis gives the raw material as 50% sophorolipid. It is believed that the material is mainly lactonic. Short chain length sophorolipids (500 micron) fibres is significant. Fibres less than 500 microns long are therefore preferred for this reason and due to the added difficulty in agitation of the longer fibres. While oxidation results in significant gross particle size reduction, this does not compensate for decreased fibril surface accessibility in the long fibres. Celluloses that have not been previously subjected to acid hydrolysis are a preferred starting material, due to reactivity, cost and resultant product dispersibility. Relatively unrefined a-cellulose, for example filter aid fibres, provides one of the most readily oxidised and dispersed sources of cellulose. An unexpected advantage of the process of the invention is the ability to use unbleached starting materials that might be regarded as unsuitable for structuring a clear liquid detergent composition. This is because the oxidation process also serves to bleach coloured components, such as lignin, in such unbleached cellulose starting materials. Because of its known specificity for primary alcohol oxidation TEMPO (and related nitroxy radical species) mediated oxidation of cellulose is preferred. The process proceeds well without cooling, at relatively high weight % cellulose in the initial suspension. Simple workup procedures afford clean material suitable for dispersion. Such TEMPO mediated oxidation of cellulose is described in the published literature and the skilled worker will be able as a matter of routine to adapt known methods to achieve the oxidation required by this invention. While aqueous NaOCI/TEMPO/NaBr is a highly preferred oxidation system. There are a number of other systems available to the skilled worker, especially for large scale production. Among such systems, there may be mentioned use of peracetic acid or monoperoxysulfate salts (Oxone®) as the oxidant with 4- acetamido-2,2,6,6- tetramethylpiperidine-1 -oxyl (4-acetamido-TEMPO) as the radical transfer catalyst or mediator and sodium bromide co-catalyst for the oxidation. Elimination of chlorine from the oxidation system is environmentally desirable. The use of 4-acetamido-TEMPO as radical transfer catalyst is also advantageous as, although it has a higher molecular weight than TEMPO, it has significantly lower vapour pressure reducing potential exposure hazards. Many other 4- substituted TEMPO analogues exist, but many, such as 4-hydroxy-TEMPO exhibit poor stability. TEMPO on solid supports or on soluble polymers may be used. Electrochemical oxidation is a potentially clean means of effecting oxidation of carbohydrate moieties, although mediation by a radical transfer catalyst (such as TEMPO) is still required. Laccase mediated oxidation, which also requires a radical transfer catalyst (e.g. TEMPO) but replaces the oxidant with an enzyme, may advantageously be used. Using the TEMPO system the degree of reproducibility of oxidation of cellulose from the same source is good. By degree of oxidisation of the modified cellulose we refer to the percentage glucose units oxidised to carboxylic acid as measured by titration with sodium hydroxide. It is assumed that all oxidation takes place at the primary alcohol positions. A reasonable assumption, given that primary alcohol specific oxidation chemistry is employed. Furthermore it is assumed that all oxidation leads to carboxylic acid formation. Degree of polymerisation (DP) does not seem greatly to influence the performance of the modified cellulose. The key thing is that the modified cellulose must remain insoluble. During oxidation, there is some degradation of the cellulose allowing release of polymer chains. It is particularly advantageous to keep this to a minimum in order to increase the yield of the modified insoluble cellulose material suitable for structuring applications. We have determined that above 70 % oxidisation, the yield is unacceptably low and the processing costs become unacceptably high. The degree of oxidation of the modified cellulose should lie in the range 10 to 70%. As the degree of oxidation increases, the amount of soluble material produced will rise and this reduces the yield of insoluble structuring material, thus the higher degrees of oxidation confer no real structuring benefits. For this reason, it is preferred to restrict the degree of oxidation to 60%, or even 50% and the most preferred modified materials have degrees of oxidation even lower than 40 or sometimes even lower than 30%. To achieve a high enough dispersibility/solubility for the modified cellulose to act as a structurant it must be oxidised to at least 10%. The exact amount of oxidation required for a minimum effect will vary according to the starting material used. Preferably, it is at least 15% oxidised and most preferably, at least 20% oxidised. At small scale, high energy sonication is the preferred method to give the high shear necessary to achieve the aqueous dispersion of the modified cellulose. However, other techniques are more suitable for large scale applications. These include the use of a high speed and high shear stirrer, or a blender, or a homogeniser. Homogenisation may achieve higher levels of dispersed material than are attainable via sonication. When degrees of oxidation of less than 10% are used, the partially oxidised cellulose proves too resistant to dispersion to produce a transparent or translucent mixture and higher energy input is required. Provided the lower limit of 10% is exceeded, those modified celluloses with a lesser degree of oxidation appear to provide greater structuring capacity once dispersed. This is attributed to less degradation of the material during oxidation and thus the existence of longer individual dispersed (not dissolved) fibrils. This may be because the structure of the cellulose starting material is partially retained, but the fibrils are rendered dispersible by the introduction of negatively charged functional groups on the surface during oxidation. Oxidised, dispersed cellulose is a largely insoluble polymer that occurs in the form of well dispersed fibrils rather than isolated solvated polymer chains. The fibrils have a large aspect ratio and are thin enough to provide almost transparent dispersions. Carboxylate groups provide anionic surface charge, which results in a degree of repulsion between fibrils, militating against their reassociation into larger structures. Addition of acid to dispersions of oxidised cellulose results in separation of gelled material while at pH between ca 5-9 fibrils may be maintained in a dispersed form as the COO- salt of an appropriate counterion. Aesthetic and Adiunct Ingredients: A wide variety of optional ingredients can be incorporated in the formulation provided they do not interfere with the mildness and foaming benefits provided by the composition. These include but are not limited to: perfumes, pearlizing and opacifying agents such as higher fatty alcohols, fatty acids, solid esters, nacreous "interference pigments" such as TiO2 coated micas, dyes and colorants, sensates such as menthol, preservatives including anti-oxidants and chelating agents, emulsion stabilizers, auxiliary thickeners, and mixtures thereof. A variety of optional additional hair or skin benefit agents may be incorporated into the compositions. However, these agents should be selected consistent with the mildness of the composition. Such benefit agents include, but are not limited to: lipids such as cholesterol, ceramides, and pseudoceramides, additional nonsilicone conditioning agents such as synthetic hydrocarbon esters, humectants such as glycerol, antimicrobial agents such as zinc pyridinethione, sunscreens, and mixtures thereof. The compositions of the invention may take the form of shampoos. These may also include minor amounts of other ingredients such as antibacterial agents, foam boosters, pearlescers, perfumes, dyes, colouring agents, preservatives, thickeners, proteins, polymers such as silicone polymers, phosphate esters, sunscreens, antidandruff agents and buffering agents. Suitable thickeners include ANTIL 141 (Goldschmidt) which has the CTFA adopted name PEG 55 propylene glycol dioleate and comprises a polyoxyethylene-propylene glycol oleate, and REWOPOL PEG 6000 DS (ex Rewo) which is a polyethylene glycol distearate. Formulation mildness to skin is a function of both lipid and protein integrity, that ensure limited trans-epidermal water loss. The stratum corneum chymotryptic enzyme (SCCE) and the stratum corneum tryptic enzyme (SCTE) are serine proteases of the kallikrein family, named KLK7/hK7 and KLK5/hK5, respectively. SCCE and SCTE are directly involved in desmosome degradation. A delicate balance between the proteolytic enzymes and their inhibitors is responsible for proper desquamation and good skin condition. We have found that blends, especially 1:1 mixtures, of sophorolipid and glycinate or sulphosuccinate offer better protein protection scores of the stratum corneum enzyme chymotrypsin than either of the single systems when added at equal concentrations. This synergy was not expected. In addition to this mildness benefit, we have also found the surfactant combination to have extremely desirable foaming properties, as discussed further below. Phase I - Mildness test (chymotrypsin pNA assay) The basis of the surfactant protein mildness detecting assay used was the enzymatic activity of Chymotrypsin on a chromogenic substrate. A harsh surfactant degrades Chymotrypsin, leading to a lower absorbance reading. Any reading greater than 0.8% is taken to be a pass for mildness. We tested non biosurfactants already described in the literature as mild together with some generally thought to be harsher, like SDS. We also tested a number of biosurfactant and other non-petrochemical surfactants. These surfactants were tested alone and in pairs. Tests were repeated with the further addition of a known naturally derived foam booster. The data includes the double system combinations in order of ranking when compared to the single system controls. Only the milder systems were explored further to determine their foaming properties. Hence, SLES/Sophorolipid (is), which was not sufficiently mild, was not explored further in terms of foaming. All the double surfactant systems performing well in mildness/ cmc/ compatibility/ green credentials were taken through to Phase 2, where they were tested for foaming. Phase 2 - Foaming test We tested all the milder surfactant combinations for foaming. The aim of the foam test was to differentiate between the foaming properties of the chosen systems on the basis of foam thickness and foam stability. Aqueous solutions of the surfactant mixtures were treated with a homogenizer, under a standard set of conditions, to create foam and then the extent and stability of the foam were assessed by turbidity measurements. The main differentiating feature was the thickness of the foam after 10 minutes compared with its initial thickness. The systems exhibiting a thicker foam that was stable over the 10 minutes, i.e. showed little sign of collapse, were ranked higher than those with a thick foam that collapsed quickly or those with only a small amount of foam. Any system that did not pass the 10 minute test was discarded as insufficiently foaming. Some, but not all, blends of the sophorolipid with other mild surfactants were found to exhibit increased mildness and foaming compared to the prior art systems using SLES/SLS surfactants as the non biosurfactant components. Example 1 For the skin protein protection assay, 70m I stock buffer solution (33mM of Tris pH8.0, 180mM of NaCI, 1mM of CaCI2) , 0m I substrate stock solution (Ala-Ala- Pro-Phe-pNA; 4 mg/ml) and 20m I enzyme (a-Chyotrypsin; 10ng per well) were added to the wells of a 96-well plate together with 10Oul of the formulations pre dicted 1: 0 in water. Reaction mixes were incubated for 45 minutes before colohmetric measurements were taken at 405nm by a SpectraMax plate reader. Natural formulations were prepared as described in Table 1. The key to the surfactant systems is given in Table 2 . Table 1 INGREDIENT % FORMULATION (w/w) Surfactant (single) 15 Surfactant (double) 15 NaCI 0.5 Table 2 Table 3 shows Single system protein protection scores for single surfactant systems. Table 3 The terms used in the tables have the following meanings: Lsmean - the least squares mean of Absorbance values for the treatment - adjusted for number of replicates or "run number" in the experiment (n=4). StdErr - the standard error for the treatment double - 1 the "extra" mildness of the treatment over the first single surfactant (e.g. ac - aa ) ; double - 2 the "extra" mildness of the treatment over the second single surfactant (e.g. ac - cc ) ; StdErr - the standard error of double - 1; tValue - the t-value to see if double - 1 is significantly different from zero; Prob - the p-value for the tValue; tValue - the t-value to see if double - 2 is significantly different from zero; Prob - the p-value for the tValue. IND = 1 if the combination is better than ALL other singles. Table 4 shows the double systems protein protection scores. In Table 4 bf ( 1 .34) is better than aa ( 1 .08), bb(1 .23), ...ss (0.53). IND = 0 if the combination is not better than all other singles (e.g. af ( 1 .13) is not better than bb ( 1 .23) and so this double cannot beat all singles). If Prob < 0.05 and IND=1 , then there is clear significance and synergistic mildness for the particular surfactant system. Thus in Table 4 the only doubles to: a) outperform all singles; and b) be significantly different from their corresponding singles are ei (Disodium Laureth Sulphosuccinate with Sophorolipid) and f i (Sodium Cocoyl Glycinate with Sophorolipid). bf = APG / glycinate. Prob. is too high for that combination. Table 4 surf Ls Std Double Std t Prob Double Std t Prob IND mean Err - 1 Err Value - 2 Err Value af 1.13 0.08 0.06 0.10 0.56 0.57 0.25 0.10 2.50 0.01 0 ai 1.21 0.08 0.14 0.10 1.40 0.16 0.28 0.10 2.89 0.00 0 bf 1.34 0.08 0.11 0.10 1.15 0.25 0.45 0.10 4.61 0.00 1 g 0.95 0.08 0.31 0.10 3.15 0.00 0.03 0.10 0.29 0.77 0 ck 0.73 0.08 0.09 0.10 0.95 0.34 0.34 0.10 3.46 0.00 0 dg 1.15 0.08 0.35 0.10 3.59 0.00 0.23 0.10 2.36 0.02 0 di 1.02 0.08 0.22 0.10 2.25 0.03 0.09 0.10 0.93 0.35 0 dk 0.85 0.08 0.04 0.10 0.43 0.66 0.45 0.10 4.62 0.00 0 ef 1.10 0.06 0.18 0.09 2.05 0.04 0.21 0.09 2.48 0.01 0 eg 1.11 0.08 0.19 0.10 1.91 0.06 0.19 0.10 1.97 0.05 0 ei 1.23 0.08 0.31 0.10 3.14 0.00 0.30 0.10 3.06 0.00 1 fg 1.11 0.08 0.22 0.10 2.21 0.03 0.74 0.10 7.48 0.00 0 f i 1.25 0.08 0.36 0.10 3.69 0.00 0.32 0.10 3.25 0.00 1 gi 1.09 0.06 0.17 0.09 2.02 0.04 0.16 0.09 1.89 0.06 0 g 0.96 0.08 0.04 0.10 0.37 0.72 0.48 0.10 4.93 0.00 0 kl 0.58 0.06 0.19 0.09 2.18 0.03 0.10 0.09 1.19 0.23 0 ks 0.62 0.06 0.23 0.09 2.64 0.01 0.09 0.08 1.18 0.24 0 is 0.67 0.06 -0.26 0.09 -3.04 0.00 0.14 0.08 1.89 0.06 0 Claims 1. A mild to the skin, foaming detergent composition comprising: a) 1 to 20 wt% sophorolipid biosurfactant, b) 1 to 20 wt% of anionic surfactant selected from the group consisting of glycinate, sulphosuccinate, and mixtures thereof, c) 0 to1 0 wt% foam boosting surfactant, d) 0 to 2 wt% additional electrolyte, e) 0 to 10 wt% additional additives, f) 40 to 98 wt% water. 2 . A composition according to claim 1, comprising cocoyl glycinate (sodium salt) as component b). 3 . A composition according to claim 1, comprising dialkoxy sulphosuccinate (disodium salt) as component b), preferably disodium laureth-3- sulphosuccinate. 4 . A composition according to any preceding claim, wherein the additional electrolyte component d) comprises sodium chloride. 5 . A composition according to any preceding claim, comprising 2 to 8 wt% foam boosting surfactant component c). 6 . A composition according to claim 5, comprising 3 to 7 wt% olivamidopropyl betaine, as foam boosting surfactant component c). 7 . A composition according to any preceding claim, wherein the additional additives e) comprise materials selected from the group: silicones, polymers, structurants thickeners, pH adjusters and mixtures thereof. A composition according to any preceding claim wherein component e) comprises 0.5 to 5 wt %, preferably 1 to 2 wt%, dispersed modified cellulose biopolymer as a structurant, wherein the modification consists of the cellulose having its C6 primary alcohols oxidised to carboxyl moieties (acid/COOH-) on 10 to 70% of the glucose units and substantially all the remainder of the C6 positions occupied by unmodified primary alcohols, Use of a mixture of 1-20 wt% sophorolipids and 1-20 wt% anionic surfactant selected from the group consisting of glycinate, sulphosuccinate, and mixtures thereof in a detergent composition to increase the mildness to the skin of the composition. Use according to claim 9, wherein the mildness to the skin of the composition is further increased by structuring the liquid with 0.5 to 5 wt %, preferably 1 to 2 wt%, dispersed modified cellulose biopolymer, wherein the modification consists of the cellulose having its C6 primary alcohols oxidised to carboxyl moieties (acid/COOH-) on 10 to 70% of the glucose units and substantially all the remainder of the C6 positions occupied by unmodified primary alcohols,