Dave Liquorice wrote:

My understanding is that this is a matter of adding two motorized
valves, one to open the HW circuit and one to open the CH circuit -
then drop in the programmer and bob's your uncle.

Or a single three way valve, depending on the plumbing and boiler this
may be an easier option. Does the boiler require a bypass if fitted
into a fully pumped system?

Easiest is definitely best. I am not sure about the bypass requirements
(what does this mean?). It is a Baxi Solo 3 50 PF (gas fired), but the
manual does not mention this.

The system is already fully pumped and is not gravity fed. I discussed
it about a month or so ago here; the setup is kind of very cheap and
non-standard, and not well known to the very helpful experts frequenting
the group. Basically there is one timeswitch which turns the entire
system on or off, and a pump for the whole caboodle. The cylinder was
fitted with a thermostatic valve and a temperature-sensitive strip. No
other controls. Needless to say, the assorted chaps on the group were
not impressed, for obvious reasons. I'm not too impressed myself either,
running the entire system when I just want enough hot water for a shower
in the morning, or heating a cylinder full of water when I just need to
run a few radiators.

When I moved into the house the termostatic valve on the cylinder was
found to be jammed mostly shut and refused to budge. My plumber as a
temporary measure removed it (I still have it here on my desk and still
can't shift it) just to get me up and running while I gave some thought
to a permanent solution up to and including the possibility of a combi.
I've decided that a combi is going to be disruptive and expensive to do
and potentially a disappointment, so I think I will stick with the
existing traditional arrangement, done up "properly" so that it is more
cost effective.

Alternatively, the present timeswitch obviously sends a control
signal up to switch on the pump which is right beside the cylinder.
I guess it just switches mains onto it. I wonder could that
arrangement be reversed;

The only box that doesn't need to be close to the valves/pump is the
room stat. Get a programable and wireless one and a single channel
wired programmer for the HW.

I am actually hoping for a single timer with fully independent control
over both systems - am I right in saying that the wiring would be a
little simpler ? I would like to be wireless everything. If stats are
necessary I will probably get a cylinder stat as well. I noticed a
programmer which I might get, that provides a temperature readout of
both systems - that's a nice touch.

"Reversing" the cable between pump and
boiler is not a problem as such but where does the system currently
pick up its mains supply?

I believe it gets it from downstairs at the timeswitch, and this is the
one possible snag in the plan. If I can do it without violating any
regulations/laws, I expect I will have to disconnect and isolate the
existing mains supply, and run mains down from the new programmer at the
cylinder, probably off the ring that the immersion heater is on.

Thanks very much for your help. If I can get the mains power question
sorted out then I think I will be armed with a plan to talk over with
the plumber.