Thanks Pete. The boiler worked fine for 12 years and was given a clean bill of health every year by the engineers from the two large organisations with whom I had a service contract (one to 2009, another since then). In July the boiler received its annual inspection and another clean bill of health. The next day it stopped working - tripped out. The service company came back, said it was a complete coincidence that it happened after their guy had "serviced" it and tried unsuccessfully to fix it. They then decided that the entire system, from gas meter through to flue, was "unsafe" and disconnected the gas, telling me I needed a new condensing boiler. When pressed, the company manager said it would be better to get the Hideaway up to standard as the condensing boiler had a limited life and might not power all our rads (big house). I contacted the builders who originally installed the Hideaway and they have attended to all the, so called, "safety issues" free of charge. They then tried to fire up the boiler again but of course it's still tripping. They have been here ages trying everything, including new gas valve and thermocouple. They spoke to Glowworm tech dept this morning and they said either the new gas valve was still faulty or the regulator was broken. Builder's plumbing engineer is coming out tomorrow to test regulator before ordering yet another gas valve. From what you say there are some more, fairly basic, checks he needs to do before going down this road. Is there any documentation that leads you through these checks as the Hideaway manual is a bit light on troubleshooting.