thanks very much for your help,
the boiler is a potterton house warmer 55 back boiler.
i have today removed the gas fire and checked the boiler details i then phoned baxi-potterton and requested a service/instalation manual .
i also checked the details of the circuit board.
the name on it...
potterton 45 or 55 back boiler.
boiler has recently started banging on igniting.
got it looked at,and it seems it is starting on full pressure when it should be a reduced pressure for the ignition.
the gas man recons it is a problem with the pcb,i was wondering if if any other part could...