"hugh" ] wrote in message
...

AIUI it is normal to have one radiator without a TRV, the one in the room
which contains the room thermostat.

Typical bodge made by plumbers.
What is needed is an auto bypass valve.

However the OPs problem is that radiators are still heating up even when
the heating is switched off but the hot water is on. This suggests as
someone has already said that a motorised valve is not switching properly.
--
hugh