Have you replaced the pcb yet and has it fully fixed the problem? I have the same boiler and think my fault lies with the pcb. Don't want to spend £150 to find out it's not the pcb though.
Alan
Alan Sterry, December 2008
Control Board Honeywell S4582D1006 BAXI SOLO 2 PF 40
Typically £130 + postage or go to a local supplier. Use Google or Yellow Pages