I have the same boiler and extactly the same problem with the pilot light not firing occasionally. My gas boiler engineer has tried to mend it many times but the problem still persists. Basically, when there is a call for heat, the orange light will come on and the ignition will try to fire the pilot light but very often it fails to do so and after 2 or 3 minutes the light will turn red and the whole thing will need to be reset again, sometimes it takes 3 or 4 goes to get it working but it may fail again the very next day, how frustrating!!!
Any ideas or ways to resolve this problem will be very much appreciated.
Matt
November 2008