Welcome to the forum dude!
Clio 172 is easily the best when it comes to corners and handling... which you would appreciate as a kart racer. But maybe not much bhp per £ when tuning. Wait - wasn't it the 172s that used to spontaneously combust?!
Punto GT... sloppy jalopy chassis but turbo tune-ability, looks good for a 15 year old car still but maybe i'm a bit biased! Italian heritage (read: reliability... haha!) but not much cult status. Simple handling improvements like Eibach anti-roll bars are like gold dust and only available second hand. Still plenty of other parts tho.
So i'd say Starlet GT all day mate Best of both worlds!
Let us know how you go