If it’s freezing then you should put the heating on even if only 30 mins to prevent burst pipes and damp. It could end up costing you more not to.
I struggle with the heating as my Lab can’t overheat due to his medication, he hates heat. I have had it on in the past and opened windows and the back door😣 for the dog.
Heated throws are 7p an hour (at the mo) if you get a large then you could all snuggle on the sofa. They heat up fast, few mins. Moving also helps, run up and down the stairs, it gets the circulation going. Have a bath, doesn’t have to be deep, share the water. You’ll use less than a shower (maybe) you’ll have to check.
If push comes to shove perhaps watch tv /books/ play board games in bed with an electric blanket.
Get a smart meter so you know how much you are using. DH is obsessed, 🙄 with his little gadget. We are currently at £100 a month for gas and electric I think. Not had heating on yet.
DH feels hot all the time, I usually feel the cold but bit peri so maybe not this year.
Our neighbours don’t appear to have conventional heating. They’re elderly and he collects wood and has mentioned an open fire place, chimney, wood on stone floor from what we gathered. No central heating. Old wooden windows. Shared bath water and they water plants with it after. This is all by choice (possibly his choice!).
You should be ok in a new build I’d have thought.
As a child we had the old fashioned gas bottle type fire in the kitchen. Depending how large your room is, they’re very handy. You can’t go over, you just use what you have in the bottle.