The heating thermostat was a nightmare. Mum had lived on her own in her bungalow for nearly 30 years and knew exactly how to operate the heating controls and then suddenly she started saying that they were broken. I got heating technicians round there and they all said that it was working perfectly. Turned out that mum had completely forgotten what to do and was either turning the heating right up, or turning it right down, or, indeed, switching the whole thing off. She was also convinced that the the thermostat controlled some sort of burglar alarm (she didnt have one). I didnt manage to get anything tamperproof organised as she wouldnt let anyone into her home, but I think that would have been the only way to stop her.