TRVs able to request heat from a zone controller in order that valves open
In scenarios like mine where a house has separate zones with valves (i.e. upstairs and downstairs) currently TRVs are effectively slaves to the zone controller thermostat which opens the valves. This means that the zone controller thermostat has to be calling for heat in order for any TRVs to work.
The ideal would be that a TRV could request heat and open the zone valve itself. Alternatively, if this is not possible, then for the TRVs to be able to call the thermostat and increase the temperature of that so it turns on, requests heat and therefore opens the zone valve.