The differences between stock and sports is the shocks and springs I believe. The difference between sport and sports plus is just springs. The hieght and firmness are different, not by huge amounts but by a little.
The
JCW suspension (optional on all cars) is lower again and firmer too.
30mm drop does not sit that low over the wheels. I have 35mm KW and its not terribly low but does catch the ground on the strenth lip under the bumper on occasion.
Try minisports eibach specials 20mm drop instead of 30mm like on normal eibachs. Firmer ride, better handling and lower too but without most of the problems the 30-50mm crowd have with clearance. Coupled with FSds they should be pretty effective.
