Hi, we moved into a new house about 5 years ago and the Potterton boiler had been installed by the builder. Ever since then we have had a lot of expensive probelms. First the mother board went and then one of the valves in the airing cupboard went. Now year later the system is making a humming noise and it sounds as thought the heating won't shut off. Even when the system is off the airing cupboard is really warm. Has another part gone and we need to call out a plumber again or should we just admit defeat and buy a new system as I think it will end up cheaper in the long run. The system is a Suprema 70L. In our last hosue we lived there for 12 years and never had a probelm. Any help you could give would be greatly appreicated.