According to our records, the alloy rims were listed as options on the 'Plus' models. The front rim (part no. 37817) was a WM1 - 21, and the rear (part no. 37809) was a WM2 - 19.
Special security bolts (part nos. 38005 & 38006) were alaso listed for use with these rims.
Regards,
Eddie.