I used to have an RSi - very fun cars, cheap insurance etc, id say more fun then my 172. I had a lot of problems with it, including:
Rust on wheel arches, Wheel bearings, suspension, electrical problems ie, immobiliser stopped working, alarm sensor had water on it due to a leaking sunroof, sunroof that never opened. The biggest problem i had was with over heating, there was a problem with the fan, and water leaks. Ah and the trim tends to fall off.
Just make sure when u take it out for a test drive, u leave the car running long enough to see if it over heats. My car would sit at a temp of about 3/4 up. Should sit about half.
Although i had all those problems, its still a great car. As long as you dont mind fixing it when it breaks....get one. I ended up selling my L reg with about 80k miles on it, for just £400