Thank you all, interesting to see what has been said, I got Energenie for last house, worked well so put old mechanic back when left and brought them with me, since Energenie were claimed to work with Nest and there was no thermostat or method to select hot water independent of central heating I fitted Nest in the main as two wires take all coms and power heat link to thermostat.
The TRV heads were paired with Nest, however it would follow using the phone to alter, but often failed to follow using set times or turning dial on Nest, so returned the TRV heads to independent control, I also bought some eQ-3 bluetooth TRV heads, and was surprised how well they worked, at £15 rather cheap, got 5 fitted upstairs and in kitchen, they are not as accurate as the Energenie I suspect as the Energenie has two sensors one for water and one for air, so is compensated for heat from radiator, but the eQ-3 has an offset so one can compensate anyway. The eQ-3 also has window open function and can be easy used without the phone, in fact they will only pair to one phone, so bluetooth is just to make setting easier. So walk into the room straight up to the TRV head press the Eco/Comfort button and room temperature steps up until next programmed change. All in all the eQ-3 seem better than the Energenie.
However this house is oil so no modulating boiler, last house gas so modulating boiler which was Bosch so no OpenTherm option, and I found the lock shield setting was critical specially when TRV fitted to return, since the Energenie shows both target and current it was a case if they over shoot close the lock shield a little, if slow reaching target open it a little, and once set there were spot on, within a degree of setting. However just can't see how a installer could afford the time needed to set lock shield valve.
As the time of fitting Energenie Hive did not have TRV heads, had Hive had TRV heads when I started I may have selected Hive, I contacted Energenie over the problems and was told Nest has withdrawn their support, so I suspect Nest will bring out their own? But unless Nest wall thermostat has fired up boiler then the TRV is useless, in the main the boiler does run once and hour at least, so the TRV heads do work, remember I am on oil so no modulation, the only time it fails is with geofencing and occupancy detection.
The thermostat is set to heat hall 0.5ºC per hour in the morning this ensures the boiler runs at least once an hour, so hall may not have hit 20ºC but all the rooms programmed to 20ºC have. The dinning room is set to heat up latter in the day, by which time the cycling of the boiler has established. However if I leave the house for over 4 hours, then on return the hall will over shoot as not now heating 0.5ºC per hour. So 2 hours after return start to feel cold as the boiler has not been running, so have to remember when we go out, chock open the internal doors so living room and hall equalise.
I assume the Hive system would not have this problem with the heat on demand system? However the Energenie did not work as advertised so why should Hive? Many advantage of electronic TRV heads is when you want 20ºC you set them to 20ºC you don't need to find out what *123456 means in real money. As to geofencing in real terms if the heating is switched off, then TRV heads do nothing, So there is no need for the TRV head to be geofencing, in fact no need for the thermostat to be geofencing either a simple sonoff would do that.
OK maybe not? If the thermostat detects how far you are from home and adjusts the temperature so further you are away the lower it is allowed to fall, and as you start to travel back it starts to increase the temperature so insuring on return it is up to comfort temperature then there is a good reason to use a thermostat not a simple switch, question is does the thermostat actually do that?
