In message , Frank Watson
writes
How to make one CH radiator come on and off at set times?
Ideally, I guess I'd like a TRV with a built-in timer - but I guess
that might be unlikely..

So what is the cheapest, simplest way to do it? It's for a bathroom
rad, which I only need on for a couple of hours in the morning.

what's wrong with just turning said radiator on/off by hand when you
need it? or is your bathroom so large that it takes a long time to warm
up? - if so getting a wall-mounted electric fan heater would be simpler

the bathroom radiator is often used as a by-pass circuit ( I think
that's the right term but if not someone will correct me) for the boiler
- if it is on your system then AIUI you shouldn't set a valve to block
it off at all.

--
dave @ stejonda