John Rumm formulated on Saturday :
I suspect they are talking nonsense or at crossed purposes. It may be that it
can't be done with the installation you have, however if you are prepared to
add controls then it looks straight forward.

All I have at the moment, is a Danfoss (I think) time clock, which sets
when CH and HW are available. A three port valve. A wireless room stat
and a wired HW cylinder stat.

The original boiler had just a live (when called) neutral and earth. I
added an extra pair in from boiler back to pump, to enable to boiler to
decide when the pump needed to be run, when the new boiler was
installed.