The ionisation PCB is available from various sources - internet or local heating engineer.. might be worth checking the ionistaion electrode ( flame detector ) first... it's in the bottom left-hand side of the burner compartment, just above the burners... if it's damaged it can cause intermittent shut down. Just follow the single grey wire up to the burners, and you'll find it...
J.R. Copley
May 2009