Thanks oilman.
the motorised valve is only 5 yrs old and is working in terms of switching between HW/CH as requested.
I've wondered whether it's the frost protection thing - but my Baxi boiler has an itegral one.
Any more thoughts?
Any suggestions would be welcome!
The pump has started running constantly - even when the system shows water and heating off. The only way to switch the thing off is to cut the main pwr to the system.
Thanks
Martin