That plugging kit looks like this one:
https://www.amazon.com/ARB-10000011-...gateway&sr=8-3[url]
Link is to Amazon in the U. S., not sure if that will work for you guys in Europe. I have that plugging kit but haven't used it on a BMW. I did use it on my Suzuki SUV and it worked well. I don't carry the case, I took the pieces out and put them in the bag of my Viair 70P compressor (12V). Even with a spare, a compressor could be very handy since they require a really high pressure and most of us do not check it real often. I have yet to have a spare in well over 40 years driving that I could not limp home on using a compressor - they have all been slow leaks. If I get a X1 or X2, however, it will have a spare. I would not expect to need it but especially on a trip, it could really save the day.
I am not a run flat fan. I believe their main purpose is to help people avoid messing with a flat. You don't have to get dirty, you can drive to the tire replace and spend a lot of money.