It's a small practice and I'm not even in the same county, so out here, if they know us, they are generally happy for us to talk through things over the phone - if they thought he definitely needed seeing today, they would have come out. They also trust my farrier, who is absolutely amazing, just sadly can't be everywhere at once.
He's more comfortable this evening, moving better, and the soreness is now localised to one heel bulb - when the pony got to this stage with one a couple of years ago, the vet took a look and said she'd lay money it would pop overnight, which it did, so hopefully better in the morning, if not there'll be someone out to him tomorrow.