With a thermostat on your tank and Y Plan not sure why you would want timed domestic hot water? With my gravity system during the summer time is the only control so no option, but with a tank thermostat it takes that long to cool down no real reason to bother turning on/off with timer, clearly want to switch off when you go on holiday, but rest of time leave it on.
As to central heating it is how many times per day? Old house 16°C over night 18°C during the day, and 20°C in evening. However this does not work in this house, as it tends to over shoot, so in the morning it moves 0.5°C per hour, so 7 temperature changes per day. My first programmable thermostat had the option of 4 changes per day, next was 6 and as far as I know there is no limit on my Nest Gen 3.
What I have found is hard wired it does not really matter how expensive, the cheap type seem to work well, in fact with a gas modulating boiler likely the cheaper type are better, but for wireless I got caught out with a Horstmann HRFS1 that lost its RF link and over heated the room, so really want one with two way coms so it fails safe. And as the price raises then very little extra to have one that connects to internet.
So with internet we have Hive, Honeywell Evo Home, Drayton Wiser, Tado, Nest, EPH etc.
So
Nest and EPH do not connect the TRV heads, but EPH you can have multi thermostats set as master slave.
Hive does not have option for OpenTherm, but the way it works with TRV heads does not need it.
EvoHome and Drayton Wiser the OpenTherm is an add on.
The Drayton Wiser TRV heads claim to work out heating rates.
it therefore seems no perfect system, what is needed is to work out which fits your home and life style best, and purse.
