My range rover recently had its mot, where they managed to lock themselves out of the car, and now the radio is not working, it wont even switch on. have checked the fuses and they are fine, could it be some keycode problem or the radio itself?

sounds very much like some silly arsed grease monkey as been fecking about, take it back and complain, no doubt it was working when you took it in to them , id they disconect the battery for any thing.