As can be seen from the graph the new thermostat seems to work as it should. And the controlling software (FHEM) now runs off a Raspberry Pi.
The red line is the set point temperature
The violet (?) line is how many percent the radiator actuator is open.
The green line is the room temperature as measured by the thermostat.
Btw. this is from today (Sunday) – and it was down to freezing last night.