noticed that boiler (baxi solo 3 pfl 70) over the past couple of nights has been making a vibrating noise now and again. this morning I went to switch on and noise appeared again. boiler is in attic. went up to discover that boiler ignites, seems to vibrate a little and switches off then ignites again a couple of seconds later. phoned plumber who installed it who said that he does not know what the problem is and cannot come out to look at it as he is not allowed to work on domestic installations anymore. looks like a gas problem and will have to call someone out. Any ideas before i do?