Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Remove room stat wires from external controls block fitted on top of control box
Place a link between the 2 connections
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Does the pump now run and the boiler recognised the CH Demand?