What cheap resturants are there in west london (west end)?

I'm looking for a resturant to go to for my 16th birthday and I want to go to one in the west end and i'm on a budget on how much I can spend in the resturants (on 5-10 friends). please give me names of resturants which are cheap (not fast food ones like macdonalds, kfc etc) and no pizza hut either.