TRV (thermostatic radiator valves Popp Zigbee 2021)

Am trying to programme a new TRV head fitted to a central heating radiator.

The TRV is fitted and working as you would expect (it maintains the room temperature as set on the ST app)

The next stage is more problematic - I only want the radiator to heat the room between two specific times.

There appears to be no instructions on how do this other than play test and see what happens!?

So far even the simplest timed routines dont appear to work

E.g. set a background temperature of 15C and enter a time when you want it to be 20C it just sits at 15C

Anyone figured out how to set a timed routine yet?