For context:
Outside it's 1 C. Guess it was quite cold last night.
Small flat, and about 11 - 12 C in the flat over night.
Cavity wall insulation, single glazing with secondary glazing
So it started from 12 C and it's now about 18 C
Used about 40 kWH so far.
I don't know if that's a lot or not. Boiler is quite old so not sure how efficient it is.