What's your thermostat set at?

Mercenary

Mine's run 24/7 in the Winter, room thermostat set at 17 - 18C. When it's warm enough in the house, whether from the radiator output or from some nicer weather with sunshine coming through the windows and heating the air somewhat, then the boiler does not run. When the temperature falls below our preferred set level, then the boiler kicks in and does it's job.
From trying both ways of using the CH over the years, we find it just as economical, and far more comfortable, to run it 24/7 with a room thermostat to cut it off when not necessary.

IMHO and from my experience, letting the house cool down to match the outside temps does take more time and effort to heat it back up to a specified level - plus the time spent shivering while waiting for it to get warmer is not pleasant. Then when the heating is switched off again the house seems quicker to lose the heat gained so temporarily.

Physics theories?.... whatever. Switching the boiler off or controlling it's function through the medium of a thermostat has the same ultimate effect....it just takes a longer or shorter period of time to get the house up to required temperature and that and the cost is all that really concerns most of us.

*ducks for cover*