thermostat set to 18C: radiator hot and room is at 23C.
How can this be rectified, so that radiator actually regulates heat, and is not constantly on?
@gthomas Unfortunately there is a number of threads on this subject but you might have some success by changing the offset - On the app>Settings>Choose the room>Temperature Offset
@gthomas are you sure the TRV was working properly before you attached the Tado head. If the pin on the TRV body is stuck or sticking then the Tado head will not calibrate properly and never close the TRV valve under normal operation.
I immediately thought of that, and checked it: The Tado valve has been in place for 5 months, so not a new installation. So still puzzling: I have also since noticed that a number of the settings have changed (e.g. "timer"), so have reset all those
Try using a pair of pliers or the face of a coin to push the pin down. There should be some resistance from an internal spring, but not stiff or jerky. A squirt of WD40 can provide a temporary fix.
Also, have you tried changing the batteries. A weak battery will result in the motor not turning fully. You cannot rely on the low battery warnings from the device/app - they have never been reliable.
Agree with GrilledCheese. 5 months old install would be right on time for new batteries.