My turtle beach PX21's are slowly dying at the moment only one speaker works and it keeps cutting out so i am in need of a new headset preferably under £50 and it would be a bonus if it worked on both PC and Xbox 360
Either Skull Candy or a Logitech, I had the G230 for a bit more than 50 pounds. Not the best but it was okay, especially if you don't feel like dishing out 300 pounds for a headset. You might have some luck checking out discount sites though, websites like click here often list sales and/or specific voucher codes for a couple of stores.
Found a list of a couple of headphones on this site by the way: click here is also among them, so I guess that's a double recommendation :)