use fresh double cream, and malibu. its the way they do it out there. coconut milk is scarce in greece as its not normally used in their cooking, i should know as im greek. they normally just use cream and malibu, and blend it with crushed ice. u can try and substutute half the cream for creamed coconut, and add a slice of pineaple to it if you want. alternatively try it
u can get tinned coconut milk almost anywhere-forget the health food shop, doubt theyd do it anyway. most corner asian/ caribbean shops and most supermarkets in the 'world foods' section