Seriously I'll have them off your hands if you like! If they are the ones in your pics then they are R90 replicas and are normally a 17" but you can get 18" versions too. Those are my favourate MINI wheels, I had a set on my old MINI. I understand the 18" works replicas to be the description for the GP replica wheels.
I would stay stick to silver wheels as white wouldn't look right and I agree that black is too much in my opinion. The OZ range is very favoured and looks brilliant. This gallery might help or hinder in your decision:
http://www.mini2.com/galleries/showgallery.php/cat/586