c55,c40 are tricky to repair,but can be repaired if economical to do so.
i will do a list of fault finding ,once i've sorted how to download pics.
im doing a list for me engineer mates.
nothing worse than getting stuck on boilers late at night.
Did you ever get round to doing that list Kestonman? Have a C40 I was at tonight where the potentiometer is only going to 20 degrees on ch. Hw pot is at 61.
New pots required?