Unfortunately, we don't have any tech info for the R61. Do you already have the door panel off and you're attempting to put the window glass into the door?
You might try going to our tech article for the R56 here:
MINI Cooper R56 Door Panel Replacement (2007-2011) | Pelican Parts DIY Maintenance Article and post a comment at the bottom. If you can include a picture of the clip you're talking about it would be appreciated. Nick might be able to assist you further.