CH Boiler had been playing up recently. Found online that my specific brand/type was prone to PCB fault.
Sure enough all signs and symptoms pointed to this fault. Ordered a complete Control Unit yesterday at 1400.
Postman delivered it at 0945 today. Removed the old unit, cleaned, then installed the new one,
All checked and fired up first time. Not bad really, as I installed the CH system nearly 15 years ago and some owner's units failed within 4 years. Not used every day though. Nice and warm now!.