Ha, what if this is the end of the thread?
Oops. Well now I've said that it clearly isn't....
Interestingly, this second attempt has started much quicker than the other, I guess basically because I didn't faff around for three days before putting it on the heat pad.
No sign of anything other than healthy yeast growth at the moment. (Watching yeast grow is a fascinating thing, btw - I often work in the study beside my ferments and got to enjoy at close range the start up fermentation of this year's batch of cider: it started with a ring of bubbles on the surface of the cider must, which quickly formed into a kind of donut shape. It formed a blanket a day after that, and then one or two days after that the blanket began to clear up and carbonation really began in earnest. Okay, maybe you had to be there....) It's clearly been spreading out from where it started this morning, when it was mostly close to the apple peel, whereas now it's covering most of the surface of the wort. The carbonation is slow (when compared with the sort of carbonation a domesticated yeast strain might be giving at this point) but steady.
Of course a mould could knock it out overnight but at the moment it's looking pretty good. I'll take it day by day.