Well, I expected to have to deal with some sort of homeowner's crisis at some point during my ownership of this house, but I hadn't really expected it to be quite this prompt.
It appears that all the electrical sockets downstairs stopped working yesterday evening, while I was out at a party. It further appears that this has nothing to do with the fusebox –
Helpfully, the power came back on around the time I got home, and then went off again shortly afterwards, which caused a number of strange beeping noises as things started up again. I assumed this was the aftermath of a brief power cut and that everything would sort itself out by morning, and went to bed. But this morning it appears I was overoptimistic.
By means of long chains of my absurd surplus of mains splitters, I've managed to emergency-