And all central heating should come from the same 230 volt supply, otherwise and UPS system to keep it running will not work. However my TRV's with this house (oil fired) have not worked anywhere near as good as with late mothers house (modulating gas) how much down to how pipework installed and how much down to on/off boiler I don't know.

I have considered changing my own thermostat, but mothers house had so many problems with wireless link, so not keen on wireless, at the moment using Nest Gen 3, as it sends info through the same two wires as it gets the 12 volt power, so all done with two wires boiler area to main house. But Nest Gen 3 does not connect to TRV heads, it said it did, but alas that's not true, but mainly the problem is house design, late mothers house worked fine without linking TRV's, but this house hall cools too slow.Turned mains supply off (& verified), removed WR1 (SCR) unit from the wall managed to prise the clips holding it together apart (without breaking any) de-soldered the old cap and re-soldered the new. Looked at Tado but info was not readily available, it seems some models not for sale in UK, same with Nest USA Nest has temperature senders but not the UK model. The red 'Receive/Alarm' light on the SCR flashes periodically for around 5 seconds every five minutes or so (which means that the Digistat and SCR are communicating) and the green light is 'on'. This means that we should be getting heat. Adjusted programmer & thermostat so that there was no heat demend, changed programmer time to come on in 5 minutes, turned Digistat up to 23C and waited.