Thats such a coincidence I also have a problem with my boiler an Apollo 15/30 and British Gas have also told me that they can't get the parts
There is obviously something funny going on!
I have been having problems with my boiler for several months now as the pilot light stays on for about 30 minutes and then goes off but it never goes on again. After repeated visits by an engineer they have told me that they have found the problem and I need the pressure switch changed however...