David Hansen wrote:

On Thu, 13 Nov 2008 14:44:03 +0000 someone who may be Edgar
wrote this:-

It'll be interesting to see what happens in the main rooms, as the rads
have TRVs. If I open them fully and rely on the room thermostat one
room could overheat while the other is still trying to get there. So it
seems I need to set the TRVs to switch off at a slightly higher
temperature than the room 'stats to limit the rise.

There would presumably be relatively little disruption in fitting a
motorised valve near each radiator, controlled by a thermostat in
that room. If the auxiliary contact on either valve, or both of
them, is calling for heat that activates the system. These two rooms
are then controlled and the other rooms will be offered heat
whenever one or both of these rooms is being heated.

Another option to consider might be the Honewell CM-zone system
http://www.cm-zone.com/application.php?language=en. It's a combination of
a CM67z wireless programmer and HR80 TRV's with radio transmitters. I've no
experience of it, we did think about it as an option a while ago and
eliminated for various reasons including cost but it is quite an ingenious
system.

--
Mike Clarke