I only seemed to get called in after the boiler has a fault. This job they were unable to keep the pilot alight. I was also informed it was serviced two years ago. When I get the boiler striped down it's just starting to soot-up that the pilot was covered in soot so the flame did not quite reach the thermocouple. The boiler went to fault mode this was pure luck. The problem when the boiler was serviced the air filter had not been cleaned and the gas jet had never been out for many years. By the time I had finished it had taken over two hours to get the boiler back up and running. The previous service must of been one of those £25 quick safety checks that had not been completed click here for what should be done on a yearly boiler service or check your boiler book under servicing. The only way I know that your boiler will be serviced correctly is contact your local registered plumber. Please note some are not registered for gas work so please check.