It's true that body condition is more important than mechanicals, but a £1000 car will always be capable of throwing you surprising bills, especially if you can't spanner it yourself.
Aside from the usual suspension fun:
1) is there a clutch somewhere in the history? Does it bite properly, or does it only engage at the top of travel?
2) Does the turbo whistle? If yes, then it is probably dying.
Other than that, assuming it drives well and you have the budget to fix what will inevitably go wrong, go for it. Don't map it unless you are prepared to put a new engine in. It may be tired, but able to do another 30K with no problems. If you turn up the boost,bit will probably break...