FWIW I cracked a rim on the M3 when I hit a pothole. It didn't seem too bad at the time - I thought I just had a flat untill I saw the crack.

I think that you are assuming more of a risk driving with the 20's - less tire wall = less cushion. Don't think you will get cash back from BMW/dealership unless good faith gesture.

Seems like wheel/tire insurance would be a good option on Irish roads

good luck