Stella went downstairs into the cellar to turn on the water heater for me (since the one in the bathroom on our floor doesn't turn on), and the main fuse went.
Thank goodness it was one you could just flip back on rather than the old melty kind you had to replace.
Interestingly enough, it wasn't the fuse for the circuit but the mean breaker. And the socket worked since the washing machine didn't mind being plugged into it.
Stella called the electrician and they said the heater was probably faulty, no wonder given its age. (Though he said he would have expected the top one to fail first. But then, that one won't even switch on.)
So I went over to Sonja's and showered there. And we'll be ordering a new heater.
Other "little" things we're considering replacing: filling up the oil tank now that prices are fairly low; replacing the windows with ones with better insulation; putting in a proper stove since the one there is really rusty (though fortunately, the oven part of it still works); converting the oil heating to gas; converting the hot water supply to be heated by the main furnace rather than separate water heaters everywhere.
Ah well. Fortunately, we're made of money so none of this will be a problem.
Also, random observation: heating on 2 seems too cold, but just one notch over 2 is fine. I wouldn't have thought that such a small change could have such a perceived difference.