If you do decide to go to non-runflats, a really cool and compact repair kit is the Slime "Smart Spair". Lots of people with Minis carry them. It would easily fit in the little compartment under the trunk. (that's where I keep my owner's manual and tire guage too.
http://www.slime.com/smartspairs/
Their office is less than a mile from my house, and I know quite a few people that work there. In fact, I just realized I know the girl in the picture on the website. (She works for them).
It's a great product. If you get a flat, you add sealant to the tire, inflate with the compressor, and then get to a tire shop. You can have the tire shop wash out the sealant (which is biodegradeable) and then repair the tire and remount.