Depends if you want a proper restaurant feel with a waiter at your beckoned call etc. If you fancy an all you can eat Chinese, I'd suggest Buffet City on Portland Street. £5.50 all you can eat, can't go wrong there! They have quite a few non-chinese dishes to choose from aswell (Chips, Omelette, Onion Rings etc). My fiance ain't a big Chinese fan, but even she likes it here. You even get Ice Cream and jelly chucked in with your £5.50 for dessert! If that don't take your fancy, then i'd go with everyone else's suggestion of Yang Sing or Little Yang Sing (just around the corner from Buffet City as it happens, right after Dawson's).