Thanks all. I'll keep an eye on it - that's what I was thinking, that the rumble should give it away before it goes into orbit (he said foolishly). I've yet to get it back in the garage and check both wheels to be sure, but if it seems OK now then I will just keep an eye on it. I've got a spare set of bearings already in drums to go on anyway, at which point the brakes might get upgraded
to the same spec as my old boat trailer, which never gave any brake trouble at all
I never leave brakes on with any trailer (or any vehicle) - if I go away on holiday the vehicles will be left in gear with handbrake off. Any brake shoe/drum left in contact usually freezes on after a while.
The persistent sticky brake is, I think, down to a mixture of a sticky cable and the fact that due to circumstances and location, the brakes get flushed and then it sits for a bit and goes in the garage, without having the benefit of a good run to dry out. The upgrade will sort that out too