Hi, whilst the boiler does work ocassionally it most often doesn't. The fan cuts in and there is a pilot light but the boiler doesn't ignite. It will keep going through this cycle until it decides to light. We have found that it will light quicker when the hot water is on at the same time. If the heating is on itslef it most often will not ignite.
Appologise if this has been listed, I did trawl through.