Think you might have trouble getting hold of these. They were effectively pulled by BMW when the
JCW stuff came out- probably to avoid a clash of interests I think.
As far as I'm aware, they are basically rebadged Eibachs, so will do the same job. I know that lavs00 has the AC Schnitzer springs on his if you want to PM him for more info (tell him I sent you

)
Good luck finding them. A while back, I think they were available from Rossiters (not sure of the address), but not sure if they still do them or not.
Hope that helps