Sounds like it could be your radiator-system thermostat ;--- should be close to the controller, in the hall-way commonly. I have had to renew one myself, and found my old one was the wrong variant for boiler-fired central heating. The old one was suited to under-floor electric, and was missing the small heater/resistor below the bi-metallic strip type of switch.
The correct type gives finer control of temperature, like a cooker simmer-stat, but the other gives coarse control. At this time of year it may not kick-in at all, unless set higher than normal room-temp. I have read on these pages that the correct thermostat needs the earth connection wired-up for it to work properly.
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