glowworm bolier that goes tick tick boom!!?

I have a glow worm boiler that lights fine initial, but whenever its tries to relight after a few hours as neccessary a tick tick noise (the lighting spark?) can be heard followed by boom (mostly likely caused by the gas building up and then lighting) I've been told to clean it but have no idea how to. Hope some one can help.
Steve Poulter, May 2006


done
Its against gas safety regulations to attempt this unless you are CORGI registered. Get in a registered installer/maintenance engineer! Be safe not sorry.

El, June 2006