C3's are good . . . . as long as it's a early chrome-bumper version. The later ones are alright but a bit more plastic looking.
They do suffer from rust to the frames and cockpit cage (which is near impossible to fix, apparently) but generally the mechanics and electrics are pretty simple and straight forward.
Although a big-block, 4-speed would be cool, I reckon that'd more like £20k, so look for a nice, simple 350 auto.