I've been a very happy user of Evohome for nearly 7 years now on my mixture of wet UFH and radiators (bought from the evohome shop
). My sister has moved into a place with wet UFH off a district heating setup (so no scope for modulating control 
). She also has a couple of towel rails that need controlling.I've been weighing up between Heatmiser and evohome and since the price is so comparable and the weather compensation/optimimum start features are proven I'll go with evohome. Since I bought my kit, some flashy new stuff like the HCC100 UFH controller and DT4 series thermostats have come out.
1. There is already some existing wiring in place, so I was thinking, can I use the DT4M thermostats with the HCC100 and evohome controller? It is not clear if the DT4M is only to be used with the HCC100 in standalone operation or if it can be used with evohome too. I like the idea of the DT4M since my sister won't have to deal with battery changes compared to the DT4R.
2. For the HCC100, since it has a heat demand relay onboard, can I use that to control the district heating exchanger (just requires a switch live) from evohome or do I have to use a BDR91 for heat demand? Again not sure if all the extra features on the HCC100 are fully compatible with evohome.
3. The other question was regarding electric heating control. For the towel rail control I was going to pick up 2x DT4R to use with some spare BDR91s I have. I understand evohome has capability for electric heating control, but my worry is that the optimum start/stop features are blanket across all the zones (I think?). For the purposes of towel rails, I want the control to be quite binary, so no clever features, just thermostatic/timer program control.
When using electric zones, do the optimum start/stop features apply to those zones in addition to the wet zones? I really don't want the towel rails coming on early etc. using unncessary electricity as they are only for drying towels and keeping the cold edge off.
Thanks in advance!