The new parts for the combi-boiler arrived today. The thermostat is in two parts: a temperature sensor (including a programmer) that I’ve positioned in our downstairs hallway, which then connects by RF to the second part: a receiving unit (switch) next to the boiler. They are now both communicating with one another and the central heating is now coming on okay. Finally, I removed the automatic air vent and replaced it. Job done! 🙂
I reckon that since we bought our new boiler in 2006 I’ve done so much repair work on it that I could set up as central heating engineer when we get back from our trip north.