I've heard great things about HeatMiser, but as you say, it does require substantial wiring to be carried out.
I personally use the HouseHeat / Conrad / ELV kit as it's wireless. I've been using it for a few years now and it's proving reliable and flexible.
Basic functionality can be achieved with the room thermostat / radiator actuator combinations, but adding the PC controller makes a huge difference since you can then get information into other HA systems as well as controlling the room thermostats.
Take a read through the HouseHeat thread further down the forum.
Martyn