Pretty sure the backs of the wheels (with / without paddles) are different, so you need to get the specific 'paddle ready' wheel.
This swedish ebay shop is well known and has been selling these for ages....you could ask them a question, see if they can help.
http://stores.ebay.co.uk/AGE-Styling...?_fsub=4126202
See here how this wheel has specific cut outs - other M Sport wheels don't have this...
http://cgi.ebay.com/ebaymotors/BMW-M...Q5fAccessories