Apparently the government is about to advise people to turn down their boiler flow temperature - claiming that that will save energy without making the house any colder.
That may be true during mild spells, allowing the boiler to run more efficiently by condensing better - but it *ain't* true for the type of cold snap which we've just been experiencing.
Unless the radiators are grossly oversized, running them cooler will reduce their output to less than is required to balance the heat losses, and the house will never reach the desired temperature.
Besides which, if people have a stored hot water system rather than a combi boiler, reducing the flow temperature too much will increase the risk of legionella.