We too are forced to keep heating on in all of the house. If we didn't we would both be crippled with rheumatismn and back-ache. And neither of us can sleep in a cold room.
IMO the whole bed needs to be well-warmed before you get into it, so either you need an electric blanket on for half-an-hour before bedtime or so many hotties that there are no cold parts of the bed.
Our heating bills are much lower than yours in the UK, or even many people around here, but even at that the rising prices are a consideration.
In your place, I would sit down and consider very seriously my entire household budget in the hope that there might be other things than heating, you could save on.
We have done the following:
cancelled magazine subscriptions
restrict our use of our telephones as much as possible
only have one lights burning in the room we are in.
use only LED bulbs
wash clothes once a fortnight instead of weekly
only use the dryer for drying bed-linen and denims
fill the oven when we bake or roast anything with dinner dishes for two or three days
drink less coffee
heat water in an old kettle on the top of the wood-burner and cook things like rice, soup etc there, after, bring things that need it (soup with meat stock and the like) to the boil on the hob
I have also hung heavy curtains in front of the outer doors and the door from the cold wash-kitchen to the rest of the house.
You may, of course, already have done all this, but I hope there may be one or two suggestions that are helpful.
I don't think you should worry about "spending your children's inheritance". I am sure they would all rather know that you are using the money sensibly to stay warm and eat nourishing food that starving yourselves and freezing.
Doubtless they would all rather that you live as long as possibe in good health than die of hypothemia, leaving them pots of money!