If you want to rent a Mini, than try to get at least a Cooper S because the Cooper, One a.s.w. are boring and even the Cooper S is an understeering car. 
There are more pleasant FWD cars on the market, like Honda Civic Type R, Peugeot 206RC or Renault Clio RS. Less understeering and between 180-200HP. Even if you don't like BMW or Porsche, I think that they are the most pleasant cars you can find at a normal rental station. Or try to arrange something with a guy here from the forum, so that he invites you to the Nürburgring and you invite him to Laguna Seca, an you share the cars, but who will borow his S2k-babe?
