I have brought home from work 3 temperature data loggers that take a temp reading every 5mins, have place them in the more colder rooms and the main hallway.
Well leave them till Tuesday and see what they say, thermostat will remain at a constant 20 degrees.
Defiantly going to buy those matches for finding draughts as I do think that even with the fan off, there are draughts that need sorting. Noticed how much the hanging Xmas decs move when there is none walking past them, so there is a draught from somewhere.
As for my windows, I have checked them but cannot see a vent at all, and if there were vents would they ever steam up? Because before I put the fan back on the did quite alot, infect the people downstairses windows are steamed up alot of the time now they have to keep them shut.