Thanks to all that provided such kind and useful advice on my indoor-weather predicament. I have to point out that, while I do doubt that my building-provided thermometer is accurate, it does say that the Rose-coloured Ranch is only a degree or two lower than the legal minimum of 21 C, and for a mysterious shining moment when I was not there but the building manager was, actually above it.
I'm pretty sure it's colder than that--I am not *such* a whiner. But reading the stories in the comments section and hearing them from other friends reminds me that I am *kind of* a whiner. My apartment has never been 12 C by any thermometer, I have never been able to see my breath inside, and all my plants are still living. I should count my blessings. So I appreciate both the advice about ovens, showers, and thermometers (which I'll likely use) and the reminder to buck up.
That said, it *does* seem a little more pleasant at my place now. This could be a morale issue, as I spent a delightful weekend abroad, but I do think it's warmer. Last night, when I returned home, if I happened to put a foot on the floor with only a sock on (my slippers sometimes fall off) it is not so terribly distressing. Mind you, I still slept rolled like a taquito in a fleece blanket (you wrap yourself standing up, then inch-worm under the normal covers) clutching a teddy bear whose floral-sachet heart can be heated in the microwave for warmth and aroma therapy. But having done all those things, I was quite warm and comfortable.
Perhaps I will be able to move on from this chilly period in my life and I actually post about a book soon. Just in case, I think I'll bake a cake tonight and leave the oven on a little extra.