Is the pilot flame well on the thermocouple? Does it stay the same size when the main burner is turned on. If not, either the pilot jet needs cleaning( dismantle on blow/suck the jet, DO NOT try to prick it out) or the regulator is faulty. Alternatively the Junkers valve in the back of the gas valve is faulty. NOTE; To work on gas appliances you need to be CORGI registered.
Daveynireland, December 2007