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A couple of recent threads have what you seek. As I recall Craven Speed are well liked. A good local company with a no questions asked return policy. I haven't done the springs yet because I can't find a mechanic I really trust to do them at a fair price.
So I just picked up my 19' Mini Cooper Clubman S ALL4 and purchased my lowering springs from ECS Tuning (Thanks ECS Tuning!) and so far AC Schnitzer is the only company that I could find that offer lowering springs. I had it installed on my car a couple of weeks ago. The ride is not as harsh as I thought it would be, but I did install Alta Performance front End Links and also GODSPEED rear control arms from ECS Tuning. But here are some pictures: