what type of corsa is it, if its a sport it will have a timeing belt, the tensioners on these can become faulty as can the rollers, best get it checked out asap as if your belt brakes so does your engine.

when i'm going along at bout 2k rpm + i can hear like a quite squeaking / rattling so i thought i'd investigate if anything was loose, but it wasn't, dunno if its a problem and just wondering if any one else had had the same 'problem'