Oned would have thought the engineers would have tried to narrow doen where the fault is but, just on case, suggest this:
Disconnect the room thermostat at the boiler to eliminate that and its wiring. If the boiler goes off, there is a fault in the termostat and / or its wiring. If the boiler doesn't go off, there is a fault in the boiler.
Reading this thread suggets it may be worth thinking about a new boiler (And not a Ravenheat one):
http://www.fixed4free.com/answers.php?id=65201
XXX
September 2016