I do like the Hive idea of "heat on demand" not sure how well it works in practice, seen some poor reports, however for it to work you also need Hive TRV heads, at just under £40 each, but the eQ-3 heads seen at £7.50 each, and if using Drayton Wiser, Honeywell EvoHome, or Tado you can actually connect to boiler using the OpenTherm which Hive does not have.
I have also made errors, I got Nest, I started with Energenie MiHome TRV heads which claimed to work with Nest, I brought them from my old house, the new house had wiring problems, and Nest can control CH and DHW and be powered by two wires, which was one reason for getting it, the other was it was claimed to work with the TRV heads I already had.
It seems when Google and Nest combined, the support was withdrawn, so my expensive TRV heads are no better in many ways to my cheap TRV heads, in some ways worst, I love NOT needing a tablet, smart phone, or PC to control the heating, the Energenie MiHome TRV heads have a single button, and it is claimed initial default temperature to 16°C. and pressing the grey push button and holding it in for two seconds boosts the eTRV to the comfort temperature setting (21°C) for one hour. But with the really cheap eQ-3 I can set what I want as Eco and Comfort and when it returns to standard settings, the really cheap TRV head in most ways is far better than the more expensive one, cheap one has window open detection and actually tells you if the valve gets stuck or the travel is too much or too little, however the expensive ones (have found at £50 a pair but needs a hub as well) actually will tell me on my phone both target and current temperature and last summer I was using them to tell me if I needed to turn on the AC before returning home, and they will by using IFTTT work with geofencing, but as to if I leave home in a hurry unexpected for long enough to be worth while I am not so sure.
Since the Nest default was to use geofencing and occupancy detection I do use it, the big thing is should we have visitors the occupancy detection ensures when we go out, they are not left in the cold, but I never bother to open app when away from home to alter temperature, I know Hive has the ability to be altered from the phone, not sure if this is automatic like with Nest or if you have to manually adjust it? I simply would never bother taking my phone out to turn up central heating, to switch on AC yes as it takes time, as not a very big AC, but central heating no.
So now back to you, for Hive to be better than what you have you will need Hive TRV heads, these are three to four times the price of programmable TRV heads which don't link to the Hive wall thermostat, you can switch anything on/off with a phone using sonoff, found at £4.03 expect postage on top of that, so to simply turn heating on/off it does not need a wifi thermostat, and in real terms that is all that is needed.
Much depends on radiator sizes, but with central heating there is no need to heat all rooms together, so if for example when you get home you start cooking a meal then set it so kitchen heats first, if you buy a meal on way home set dinning room first, and if you sit back for a time then living room first, and heating one room at a time you can heat rooms very fast, as long as radiator is big enough, why any house has zone valves for heating I have not worked out, the TRV does a far better job with programmable heads, they are really zone valves, except unless linked to wall thermostat they don't start the boiler.
I cheat, my dining room is set to start warming up at 4 pm, so at 3 pm the wall thermostat reduces temperature, and at 4 pm it increases again so boiler is running at 4 pm. No wifi links, just set the times.
