Hi, I have just bought a C2 GT from a private seller who is currently on holiday so I can't get hold of him. The strange thing is, I can't seem to find reverse! The gearbox seems pretty standard until you reach 5th gear, which rather than being located in the top right of the gearbox, is actually in the bottom right. In place of where 5th normally is, is a gear that seems more like 3rd from the amount of revs I was getting when changing into it from 4th. I have tried messing about with the gears when stationary but seriously can't work out where reverse is!
Any help would be seriously appreciated.

I'm not personally familiar with the Citroen gearbox, but I do know some Euro transmissions have a reverse lock-out feature that requires you to either press down or to lift up on the shifter to engage reverse. Kind of a safety feature to prevent accidental reverse engagement while moving forward.
Again, I don't know that your's actually has that feature, just a thought.
You may also want to find a trans shop to analyze the gear ratios for that fifth gear issue.
Good luck. I hope this helps.