FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) HAIR CARE COMPOSITIONS HINDUSTAN UNILEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India The following specification particularly describes the invention and the manner in which it is to be performed HAIR CARE COMPOSITIONS FIELD OF THE INVENTION This invention relates to hair care compositions incorporating aikyl modified silicones. BACKGROUND AND PRIOR ART Alkyl modified silicones have found application within a range of cosmetic products, particularly as moisturisers in skin care products and as spreading agents in sunscreens. WO91/09586 describes how certain polymethylalkylsiloxanes can provide hair with improved shine and gloss as well as superior manageability and a soft feel in the same manner as polydimethylsiloxanes, but which also leave the hair feeling less coated and greasy in appearance. These polymethylalkylsiloxanes are also claimed to leave the hair with more body, fullness and softness relative to polydimethylsiloxane fluids. The present inventors have observed that alkyl modified silicones of the type disclosed in WO91/09586 have a tendency to deposit excessively onto the hair when used in a conventional hair conditioner base. Excessive deposition is correlated with reduced hair volume, which is perceived by many consumers as undesirable. The present inventors have found that these problems can be solved by combining emulsified particles of the alkyl modified silicone with emulsified particles of certain non-alkyl modified silicones. SUMMARY OF THE INVENTION The present invention provides a hair care composition comprising: (i) emulsified particles of an alkyl modified silicone, and (ii) emulsified particles of a non-volatile, non-alkyl modified silicone. Compositions according to the invention deliver effective conditioning to the hair, without unacceptably high deposition. DETAILED DESCRIPTION Alkyl modified silicone The hair care composition of the invention comprises emulsified particles of an alkyl modified silicone. By "alkyl modified silicone" is generally meant an organosiloxane polymer in which at least one pendant alkyl group having a hydrocarbyl chain length of C6 or greater extends from at least one of the silicon atoms forming the polymer backbone. The physical form of alkyl modified silicones under ambient conditions generally varies from wax to fluid depending on molecular parameters such as the chain length of the alkyl group, number of alkyl groups (other than methyl) in the molecule and silicone backbone molecular weight. The term "ambient conditions" as used herein refers to surrounding conditions at one atmosphere of pressure, 50% relative humidity, and 25°C. Preferred alkyl modified silicones for use in the invention are fluids under ambient conditions. Preferred alkyl modified silicones for use in the invention have a number average molecular weight (Mn) ranging from 10,000 to 450,000, more preferably from 60,000 to 110,000 dalton. Suitable alkyl modified silicones for use in the hair care compositions of the invention may be chemically characterised by the general formula (I): (CH3)3Si-O-[Si(CH3) (R)O]m-[Si(CH3)20]n-Si(CH3)3 (I) in which m has a value of 1 to 450, n has a value of 1 to 3000 and R is a monovalent alkyl radical of from 8 to 60 carbon atoms. In general formula (I), the -[Si(CH3) 2O] - units are typically randomly interspersed with the -[Si(CH3> (R8) in which n is 1 to 7 and Rlf R2, R3, RA, RS, Re, R7, and R3 are independently selected from Ci-Cs alkyl, aryl (especially phenyl), and alkaryl (e.g. Ci-Cs substituted aryl). Preferably R1, R2, R3, R4, Rs, Re/ R7, and Rs are Ci-C2 alkyl. Most preferably Ri, R2, R3, R4, R5, Re/ R7/ and Rs are Ci alkyl (such materials have the CTFA designation dimethicone). Silicones of the above described types are commercially available, for example from Dow Corning Corporation as DC 244, 245, 344, 345 and 200 fluids. Other Optional Ingredients A composition of the invention may contain other ingredients for enhancing performance and/or consumer acceptability. Such ingredients include fragrance, dyes and pigments, pH adjusting agents, pearlescers or opacifiers, viscosity modifiers, preservatives, and natural hair nutrients such as botanicals, fruit extracts, sugar derivatives and amino acids. Mode of Use The compositions of the invention are primarily intended for topical application to the hair and/or scalp of a human subject in rinse-off compositions, in order to improve hair fibre surface properties such as hair fibre lubrication, smoothness, softness, manageability, alignment, and shine. The compositions provided by the invention are preferably conditioner compositions for the treatment of hair (typically after shampooing) and subsequent rinsing. Alternatively the compositions provided by the invention may be aqueous shampoo compositions, used by massaging them into the hair followed by rinsing with clean water prior to drying the hair. Optionally, a separate conditioning formulation may be applied after rinsing and before drying, but this may not be necessary as an aqueous shampoo composition of this invention is intended to provide both cleansing and conditioning to the hair. The invention is further illustrated with reference to the following, non-limiting examples, in which all percentages are by weight based on total weight unless otherwise specified. Examples according to the invention are indicated by a number. Comparative examples (not according to the invention) are indicated by a letter. EXAMPLES Hair conditioner formulations were prepared having ingredients as shown in the following Table 1: Table 1 Ingredient Ex.1 Ex.2 Ex. A Ex.B Ex.C Ex.D Ex.E Ex.F Ex.G ARQUAD® 16-50(1> 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 ARQUAE® 2HT<2> 1.07 1.07 1.07 1.07 1.07 1.07 1.07 1.07 1.07 Cetostearyl alcohol 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 Alfcyl- modified silicone13' 0.77 1.54 4.62 7.69 Alkyl-modified silicone'4' 0.77 1.54 4.62 7.69 DOW CORNING® 1785 Emulsion'5' 4.17 4.17 5 Water, minors q.s. q.s . q.s. q.s. q.s. q.s. q.s. q.s. q.s. (1) Cetrimonium chloride (50wt% a.i.). (21 Di (hydrogenated tallow) dimethylammonium chloride (75wt% a.i.) (3) Emulsion (65wt% a.i., with non-ionic surfactant) of an alkyl modified silicone of formula (I) above in which R is a C12 linear alkyl radical, m is 75 and n is 1150 (from Momentive Performance Materials, Inc.). (J!) Emulsion (65wt% a.i., with non-ionic surfactant) of an alkyl modified silicone of formula. (I) above in which R is a C12 linear alkyl radical,, m is 50 and n is 770 (from Momentive Performance Materials, Inc.). (5) Emulsion (60wt% a.i., with anionic; surfactant) of dixiethiconol. The formulations of Table 1 were evaluated for their ability to align hair and for their silicon deposition on hair. For the hair alignment study, the test formulation is applied to hair switches of a standard mass and dimension of hair. Photographs are generated once these switches have been dried under controlled conditions. Panellists are asked to make paired comparisons of the. degree of misalignment of the switches in these photographs against a fixed reference image. 3 6 comparisons are made for each test formulation. Silicon deposition was measured by X-ray fluorescence spectroscopy. The volume of the hair switches after treatment with the test formulations was also assessed. The results of the above analyses are shown in the following Table 2; Table 2 Test Measurement Ex.1 Ex.2 Ex. A Ex.B Ex.C Ex.D Ex.E Ex.F Ex.G Misalignment panel score 0.993 1.075 1,316 1.009 0.977 1.278 1.322 0.943 1.3B2 Standard error of misalignment panel score 0.054 0.031 0.046 0.06 0.046 0.06 0.046 0.06 0.045 Silicon deposition (ppm) 1061 271 484 1740 11835 577 1916 6544 214 Standard deviation of silicon deposition 565 84 87 307 6947 175 592 972 200 Switch volume (mm^) 8647.57 10023.32 10888.68 6950.78 1253.22 10501.79 7025.24 1852.81 10256.67 Standard deviation of switch volume 1238.66 659.84 694.21 1079.5 129.66 1047.74 1439.31 525.53 977.29 For hair misalignment, a lower score is preferred. It is also desirable to avoid excessive levels of silicone deposition on the hair. It can be seen from the above data how high levels of silicon deposition correlate with a reduced switch volume. Example 1 (according to the invention) and Examples A to C (comparatives) all employ alkyl modified silicone (3> at various active levels. Within this series, Example 1 and Example C provide the best (i.e. lowest) hair misalignment scores. However, Example C demonstrates an undesirable 11-fold increase in silicon deposition on the hair, and significantly reduced switch volume, relative to Example 1. Example 2 (according to the invention) and Examples D to F (comparatives) all employ alkyl modified silicone (4) at various active levels. Within this series, Example 2 and Example F provide the best (i.e. lowest) hair misalignment scores. However, Example F demonstrates an undesirable 24-fold increase in silicon deposition, and significantly reduced switch volume, relative to Example 2. Comparative Example G gives a level of silicon deposition which is approximately equivalent to that of Example 2. However the performance of Example G on hair misalignment is significantly inferior to that of Example 2. Therefore the formulations of the invention provide a superior balance of hair alignment, silicon deposition and hair volume relative to the comparative examples. CLAIMS 1. A hair care composition comprising: (i) emulsified particles of an alkyl modified silicone, and (ii) emulsified particles of a non-volatile, non-alky1 modified silicone, characerised in that the alkyl modified silicone has the general formula (I) : (CH3)3Si-O-[Si(CH3) (R)O]m-[Si(CH3)2O]n-Si(CH3)3 (D in which m has a value of 1 to 450, n has a value of I to 3000 and R is a monovalent alkyl radical of from 8 to 60 carbon atoms. 2. A composition according to claim 1, in which R is a linear alkyl radical having from 10 to 12 carbon atoms. 3. A composition according to any one of claims 1 to 2, ir which the non-volatile, non-alkyl modified silicone ha= the general formula (II): A(R)zSi-O-[Si {R)2-O)x-Si(R)2A (II) in which each R is independently selected from C1-4 alkyl or aryl, x is an integer from 200 to 8,000 and each A is independently selected from C1-4 alkyl, C1-4 alkoxy, aryl, aryloxy or hydroxyl. 4. A composition according to claim 3, in which all R groups are methyl and both A groups are hydroxyl. 5. A composition according to any one of claims 1 to 4, in which the weight ratio of alkyl modified silicone to non-volatile, non-alkyl modified silicone ranges from 1:2 to 1:6. 6. A composition according to any one of claims 1 to 5, which is in the form of a conditioner for the treatment of hair (after shampooing) and subsequent rinsing.