Hi John,

I have managed to sort it all out at last :-)

I have numerous times powered the whole system down (including the
boiler) whilst working on it and trying to sort it out and the boiler
would reboot every time.

The only thing I have never touched since the boiler was installed, is
the boilers code protected installer settings'. Late yesterday evening
I thought why not - so I set it to do a factory restore of the settings
and a reboot. After which both CH & HW behaved perfectly, apart from a
bit of cycling on just producing HW, because the boiler was producing
too much heat Kw for the cylinder - adjustable for Kw on d.77

It has done two more HW calls today and both worked perfectly. Thank
you very much indeed for your help on this..