Lorien,
Are the MIchelins that much quieter than the runflats?
The 'investment" here in the US is $192 each plus shipping/mounting/balancing. That's about 102 GBP each plus/plus/plus. You paid the equivalent of $267 per tire.
For peace of mind, I recommend the Continental Comfort Kit. I have one in my MINIs that have non-runflats. They're available from the Tire Rack here in the US; and I'm sure they're in Europe as well. Here's the Tire Rack link.
Tire Accessories - Continental Tire ContiComfortKit
If you'd like, I'll check and see if it fits in one of the 2 pockets in the rear under the storage area.
Charlie