Yes, the boiler & Pi are inside a cupboard. The sensor is accurate, it’s the room that is very warm. Sadly it’s not even a linear relationship to the rest of the house - if the hot water needs to come on, then that will raise the temp in the cupboard without heating the house.
Sorry, that was unclear, I’ll update the text. I can of course boost the water (that’s covered in my MQTT post), the key word here is “on”, not “heating”. The issue is that I couldn’t find a way to cancel the boost (i.e. turn the heating off) - all my attempts to do so didn’t work. Although now I think about it, perhaps sending a new boost with a duration of 1 minute would be almost the same thing… Anyway, letting the boost finish is a neat way of avoiding heating oscillations