Hi all, I have a Worcester Greenstar Heatslave 18/25 oil boiler that is faulty. Basically, the heating won't work when called for and the hot water only works when the boiler is given a tap/bang on the top. That said, once the boiler comes to life, with the heating selected and the hot water de-selected, the boiler is running but not heating the radiators. The boiler then stops and then restarts itself. Once this has happened the radiators start to heat up and the boiler seems to run fine. We had the boiler serviced in the spring but not used the central heating much since then I don't think. Any suggestion what the problem might be?