Following up, I had a to-and-fro with their customer services team, who confirmed FedEx options come with full tracking and insurance. So I ordered four Image HCs that are unavailable until the UK, and even with the shipping costs taken into account wouldn’t end up costing me extra. (I also finally grabbed Mr Higgins Comes Home, which is usually £10–15 in the UK but currently $9 there, and weighs bigger all, and so doesn’t increase the shipping costs.)
I can’t imagine I’ll use them much. I prefer Hive/Reed/etc. But as a one-off, here’s hoping it all works.