I thought the Multi Function Sterring wheel was already out for new mini's. As for having it fitted after you've bought it I'm not 100% sure but here is what I do know.
BMW retro fit Multi Function Sterring wheels to their other cars.
I have an acceessories Price/Part No's/Availabilty List on an Excel file I downloaded of this website somewhere (i'll try find it). In it had the option "Retro Fitted Multifunction steering wheel" It said Availability: In Testing, and I may be wrong but I'm almost positive the price was around the (are you ready for this?) £600! Weather that includes fitting aswell i don't know!
I'll try and find the excel file and I'll post a link!
I think the MFSW is really good. I bought it for the stereo controls tho to be honest, and don't do enough motorway miles to necessarily justify the cruise...
BUT now the M11 is all dug up and 40mph with gatsos for miles, the cruise is ace - just set it at 40 and relax. Not only that but I doubt the novelty of being able to accelerate using my thumb will ever wear off!