Ooh, I like a bit of a discussion. :)
Basically we're trying to eke out our savings which is what we're mainly living off. I'm a SAHM and DH is a student who gets occasional contract work. So it's stuff like food and electricity, nothing fancy, but we wouldn't be forced to starve if we turned the heating on.
We're trying to maintain our savings so I can stay at home with DS for as long as possible (we'd ideally like to educate him at home if we can). DH will almost certainly be in fairly low-paid work once he finishes studying and there will probably come a point when his salary won't be enough to cover our living costs.
We've trained ourselves to be hardy here.
My view is that most of the world / most people throughout of history don't have heating in their bedrooms so it's not that big a deal. It's only like giving your child a nap in the pram while you're out for a walk. Incidentally, our house was built in the 1930s with fireplaces - but only downstairs.
Actually, I feel the cold more than most people I know. I used to use hot water bottles a lot but since wearing more thin layers, I find I don't need them any more.
The rest of the house is considerably warmer, especially when we use the oven, which we often do in winter.
We do put the heating on if anyone's ill, or if we have vistors. A previous flat of ours had ice on the inside of the windows even after running the heating, so this doesn't seem too bad by comparison.
Sadly there isn't another room big enough for our co-sleeping arrangement.
Unfortunately we have to heat 2 other rooms if we want to put the loft radiator on, and it's the furthest room from the boiler, so it doesn't get as hot as the other radiators.
The loft conversion is only 4 or 5 years old, so the insulation isn't too bad, and it's double glazed. In the winter the snow stays longer on our roof than on our neighbours without loft conversions, which suggests we lose less heat through the roof then they do.
I'll add a fleece sleepsuit tomorrow and see if it makes a difference. I might dig out one of our spare duvets and see what DS makes of it.
Now I just need a solution to DS's bursts of flatulence waking him up. 