Issue with constant heating demand

Hi and firstly thanks for a fantastic site as it's rather helpfull.

Boilermate 2000 with a Glow Worm Micron 50.
Problem being the Central Heating constantly on with no demand for heat from the Room Stat.

Room Stat disconnected and still a call for Heat to the Boiler.
Boiler 'switched live wire' (#7) disconnected and proves the call for heat is from the Boilermate and not the Boiler.

Phone Gledhills Tech line and the chap on the line was adamant it was the Boiler or a circulation issue.. his claim was the fact the Boilermate will be calling for Heat to satisfiy it's needs to keep it above 65* and the Boiler 'heat exchanger' may be blocked or pump running poorly preventing the supply Temps from reaching it's required values of 65+* so the Boilermate will keep calling for Heat!
He kept me on the me on the phone for over 20 mins trying to convince me this is the problem.

As a side note the Boiler at no time has ever been cycling or overheat trip off etc, so I cannot believe his therory of the exchanger or poor circulation being the cause.
I believe it's the ACB or PCB (whatever it's called now)

Can anyone shed some light or offer suggestions. (I can provide more info if required)

Regards
Dave

It is your main control board or PCB
Mike
MGC/H2O
Norfolk

Thank you Mike...

I will replace the Board and report further.

Best Regards
Dave