Hello Mate
I have a 1992 K plate so one of the first and before I had bought it it had never really been looked after. Hence it needed a full repaint. But when I took the body parts off to paint them I found no rust at all!
As with the previous comments there are a few rusty ones but in general I think they have survived quite well. If you can get it on a ramp and have a good look before you part with the hard cash then it is a good idea. I spent about half an hour under mine before I habded over the money!
Paul