roberth1 wrote:

Thought the anwer would be to get a wireless programmable digital
thermostat but on reading all the installation instructions vial
downloads none of them appear to be able to send a signal to just have
HW on like in the summer time for example.

The wireless stat only controls the CH, not the HW. The HW would still
be controlled by the timer (and also a HW stat which is really just
there to shut off the boiler, to stop the water getting too hot).

I did exactly what you are describing recently. I got a two-channel
clock (Honeywell ST6400C) and a wireless stat (Honeywell CM67). The
ST6400C turns the hot water on or off independently of the room stat
turning the heating on and off. On the ST6400 timeclock I've programmed
the heating to be "always on"; the CM67 is connected in series so the
heating is only on when the stat requests it.

The secret to making it all work is to get a mid-position three-port valve.

It would be very handy to have a stat combined with a wireless
programmer which would allow you to control everything from one place,
but nobody seems to make anything like this.

In my case it would just
mean a signal to activate the boiler to "on" as the HW would then be
heated.
I do not have a problem with the upstairs rads getting hot as these are
all fitted with thermo valves.

Yeah, but that's not as efficient as having more precise control, which
you can have by marrying a two-channel programmer and a stat as
described above.