After my third sidewall puncture caused by the fabulous potholes on our roads, probably my fault as well as I am running 20s, I decided enough was enough and I would do whatever it would take to get a spare.
Alpina UK originally said a space saver kit did not exist for the D4. Alloy Wheels Direct with consultation with Alpina also said the same. So Jonathan at Alpina said try BMW space saver kit type D, 18" fits a 5 GT and 7 series bought from Alloy W D for £344, BMW price is £428.
I have just had a trial fit by the kind people at Lodge Birmingham, I've spent some money with them! and it fits with no issues at all.
So I would think it would fit all F3X cars but probably not suitable for X-drive. The diameter difference is 6mm which should not make any difference to anything mechanical on the way home at 50mph. I will probably now never need it. I can still fit the clubs and trolley in the boot which I wouldn't have been able to do with a full size spare.
It will be transferred to my next D4.
Duncan