Max Demian explained :
I use a much lower temperature as I don't have a room thermostat and the TRVs
are fiddly and don't seem to keep the air temperature constant.

That is at odds with my own findings, since installing TRV's last
March, but I do have a room stat, in the hall and no TRV on just that
one rad.

I tried setting the TRV's up in March for each room, but there wasn't
much need for heat at all then. I found it better to set them once the
cold weather arrived this winter. Having gradually tweaked each to a
comfortable temperature, they work pretty well. Working on just a room
stat, the temperature variation was quite noticeable as the boiler
kicked in and out on just the room stat..