Phew!
Thank you everyone for holding my hand there. I'm relieved I've done it, because if I hadn't I'd still be fretting about it. Now I can relax until they ship.
JAileen: Basic risk is the nominal shipping cost. This is worth it for the chance to try on a pair of shoes I've been obsessed with since they hit the catwalk in 2008. Yeah, I looked it up. So not quite ten years, but a very long time. Opportunity cost is probably the handbag I was thinking of buying, a purchase I can defer until later in the year.
I've been looking at them again online and I'm still concerned about the heel height. A good pair of heels can be surprisingly comfortable, but if I'm not happy then back they go.