wow. I brought the temp of the room down a touch (from 72 to 70) and today, just as I was prepared to swirly gently, etc., it is active again. Airlock popping about once every 45 secs or so: a very reassuring sign. Now I suppose I'll just leave for another week.
I see why monks were good at this: it takes unearthly patience and trust in something you can't see.
Thanks for the advice everyone