if you go to Boots.. at the mo they are doing a 'free' assessment of your face and the best foundation for your skin type and your skin type - then you will be able to decide on how much you want to spend on you!
believe me, i am the queen of cosmetics. its my hobby, i have darkish skin and i find that every foundation is pinkish based...i want a yellow based foundation. who wants a bloody pink face??? the best ones i think are kenebo (quite expensive but yellow based as asian make) but i must admit, i always go back to M&S foundation...its smashing and a great colour and price.