Over the years my potterton combi boiler has become annoyingly loud that when boiler is on it makes me want to turn it off. Sometimes there is a slightly different pitch to the noise and I can get rid of that noise by just compressing something against the side of cover of the boiler this temporarily stops the vibration kind of noise. But the loud humming noise is always there. I have boiler cover but last time I mentioned it they said they can't do anything about that but it's so loud that even my neighbours can hear my boiler lol. Is there anything they can check?