I was going to post this in the real gas post but maybe you can use the info for your future purchase. BTW, I have a '02 VW Beetle diesel, plenty of power and great fuel economy (45 mpg) and its fun enough. My girlfriends sister has had 2 mini coopers, 1 convertible 1 hardtop, and they were both awesome. And with one of those, your bike could snuggle up to it in their own little British way
http://finance.yahoo.com/loans/article/104365/Diesels-Image-Crisis