Dave Plowman (News) has brought this to us :
Never did understand why so many pros used to fit the main stat in the
hall. Just were opening the front door can lower the temperature of that
area.

Our stat is in the hall. During the original refurb many years ago it
was wired to be located in the living room, but I insisted it be placed
in the hall - just a matter of poking the cable through the wall.
Present stat is a wireless stat, so could be located anywhere.

The hall has the front door, but the front door is not often used, so
it is mostly an enclosed space with a radiator.