Hi. Im a new member with a problem (my expertise is AV so ill help out as much as I can there!) Ive had a Worcester Bosch 240 boiler for nearly 15 years and had it serviced by BG yearly. Earlier this year it developed a problem whereas the overheat switch would pop as I filled the bath (usually around 1/3rd full) It would be fine with the central heating or running the shower or sink etc.....The water would alwazs get hot. BG were called out to solve the problem and swapped the thermostat cut of sensor plus a couple of other small items. After they left the problem was still present so an engineer returned and fitted a new circuit board and adjusted a few settings.....He also added an earthing cable (which incidentally he did not sleeve....naughty!) Anyway the problem was still present but I managed to find a way of filling the bath without the overheat tripping ( I would run the bath for a minute or so, stop it for a minute and then repeat..eventually I would get my bath!) However now whenever you try and run the hot water it takes an age for the boiler to fire...I mean like 5 minutes. You can hear the piezo clicking away but it doesnt fire, after a while it fires and runs hot for a few minutes then goes out.....If left running it tries to ignite and after another few minutes it fires again but soon goes out etc. A total nightmare if you are trying to have a shower! BG have told me the system needs flushing which will cost over £500 but the engineer didnt seem at all convinced that would cure the problem! Any ideas as to what it might be? Thanks in anticipation.