The more I think about it the more I know I'm going to regret falling for that BMW spiel and not going for normal tyres. I imagine the next time I get a puncture it seems I'm destined to have to hunt around to get another tyre - a dealer told me they'll always be in short supply so best to buy a couple and keep them in the garage!
As for the RAC insurance - yes that's interesting - but I don't suppose they would let me do that (keep spares). So imagine - the only RFT's available are Bridgestone - I have to replace both Michelins to get a pair - would the insurance pay for two tyres when only one punctured? I doubt it