Much of what I could think of would be along the lines of what the other lads said with rust being one of the major points. Rust on the body and also on the steel brake lines can be expensive fixes, the brake lines will be an NCT fail.
On the coupe it's worth checking that the windows pop down when the door is opened and go back up when the door is closed. If they don't the problem is the micro switch in the door strike and solved by a trip to the dealer for a €50 part.
With the M44 engine a lot of poor running can be traced back to vacuum leaks and can be simple enough fixes. Also the coolant system on these cars can be due for a refresh so worth adding into the budget