how can I fix my central heating boiler?

I have a Ferolli 77CF combi bolier 1993. If we turn on the hot water we have to continually hold down the pilot and eventually it will ignite the gas - we then get hot water and radiators on. As soon as you try and use the hot water again it has all shut down and needs you to hold down the ignition - this can take up to 10 mins. We had a repair mn out who said it was the pump - we had it repaired - no change. They then said it was the PCB - £182.50 for the part and still no joy. Please any advice - could it be to do with the gas feed? I am desperate and freezing.

Caroline Howard
January 2006