Thanks guys,

I think I will try and clean out / flush the system, check the pump is
starting whe it is supposed to and go from there.

I have eleven rads in the house, all of which get hot nicely but none
have TRVs. I am going to install 9 trv's and leave them off the small
rad in the en suite shower room (I think it might be the bypass as it
comes on with HW or with CH) and the rad in the entrance hall (this is
always a cold room and the room stat is installed here - I have read
the trv and stat *may* interfere with eachother).

How much of a pain is the flushing? Is it worth trying to install all
9 valves in one hit when the system is empty?. Also I would like to
move a downstairs radiator a foot or so in order that I can make a new
internal doorway - as this means digging up the concrete do you think
I should try and do it all at once?

Thanks for the help it is much appreciated and I wait for the day that
someone asks a Q on here that I have the answer to ;o)

Tim