I'm afraid I don't know of any offhand, MuleSkinner. I know that Hasslefree has some kind of arrangement with Armorcast and they do carry some Armorcast items. You might contact Sally at Hasslefree and see if she can maybe order you some with the next restock.
Otherwise I would email Matt at Armorcast and ask him. His address (from their website) is matt@armorcast.com. I'll wager somebody stocks at least part of their line in the UK, since it's really nice stuff.