I found the
T4R manual and also note the
CM 927 is more expensive so one would expect more features.
I did some thing similar not wireless in my case, but I swapped thermostat due to old one going faulty, and old one really easy to override and new one had to keep book with thermostat to change temp as so complex.
I am not a lover of my Nest Gen 3, it is rather poor as one can't link TRV heads to it, however it has a large display, and easy to turn up or down manually without altering the back ground program.
I am looking for a second thermostat myself, and it does seem Hive is around the cheapest with will connect to TRV heads, in the Honeywell range we are looking at £300 for the EvoHome, with Drayton wiser it depends if you need DHW control, Tado it seems UK models do not connect to TRV heads so although they do a model which can, it needs to be got from internet.
It does seem to be a nightmare selecting both wall thermostats and TRV heads, made a mistake with latter, looked so good
but then found only way to control is with a hub and on internet, no way to manually control, this
far cheaper unit worked so much better, can walk into a room press one button and either simply turn between eco and comfort settings or run boost, can use phone with bluetooth, but also manual controls. This one
does far more than other two, at £35 more expensive than the £15 spent on the eQ-3 models but cheaper than the Energenie and can be manual controlled. To get a linked TRV head jumping to £50.
Where do we stop? and is the extra control worth it? I really don't know, I decided I would not upgrade my system until the summer, if some thing goes wrong, I want time to correct, seems likely I will opt for Wiser. But I look at Hive
and think why pay more? But the range goes to £149.99 and one asks the question what more does it do? It is the small print like "Hub required for app use and hot water control (sold separately)" and one thinks hang on, it says "Hubless" and it seems it uses a zigbee hub and I already have one of those. But will it work?
So your not the only one who feels bamboozled by all this technically talk, I have been caught out once with Nest, which seemed the bees knees, and don't want to get it wrong a second time. I have the old TRV head where I intend to fit second wall thermostat, at the moment showing
the one which replaced it after the carpet fitters damaged it is showing
so 19.1ºC v 22ºC in same room, it shows a lovely report
but how does that help? The TRV shows a better report to the Nest Gen 3 wall thermostat even if 1/5th of the price. It all seems daft.