Is there a thermostat on the hot water cylinder? If yes, does it do anything (ie if the hot water is cool, boiler is running heating water only (in theory) does turning the stat down to 15 or so cause the boiler to switch off?
Final Q for now- exactly which Sensohome controller do you have?
Yes there is a thermostat and yes it appears to work as we have adjusted it due to tap water being too hot. I need to try to check it switches the boiler off though but didn't catch the boiler this morning before it heated the water.
The SensoHome is the wired in one VRT380.