Due to a long, outrageous story featuring bad luck, an ageing system, poor workmanship and cowboy traders (which I won't go into), we lost our central heating entirely 3 years ago. Spent a whole year with no heating except for a couple of electric convector heaters and a mobile Calor gas fire. We gave in and installed independent electric heaters in every room (they look like slim, elegant storage heaters but don't rely on heat bricks inside). That was disruptive and colossally expensive (and also brought its own share of rogues out of the woodwork) but, now it's done and over with, we're glad we did it. Each heater is easily removable from the wall (unlike plumbed-in water- or oil-filled radiators) so we can take them with us if we move. Each one is separately programmable, so we can have however much heat we want where we want and when we want (different for each room). I can't say how much it affected us financially because energy costs went mad at the time we were changing over - the house is now all-electric (which has own drawbacks, but we're pretty well-prepared with emergency measures in place to cope with power cuts).
We both grew up in old houses with just a fireplace in each room (in my childhood home, the bedroom fireplaces were boarded up!) so we learned early on how to keep warm without mollycoddling!
1. Thermal underwear.
2. Lots of clothing layers (one thick jumper doesn't work anywhere near as well as three thinner ones).
3. Fleece beanies, gloves and socks.
4. Blankets (again, fleece ones are pretty good).
5. Hot drinks.
6. Common sense.
7. Using other buildings which were heated. Shove a trolley around a supermarket for an hour. Visit the library (heat, armchairs and something to read - how bad can that be?).
Use coffee shops that don't hassle you to leave after one cup (having a book, tablet and notepad makes a good image - they thought we were writers!).
During the fuel crisis, some people created a heat-sharing group, visiting each other's houses in turn for chat and dinner. Humans can be ingenious when the chips are down.