We had the nest installed but the ch wouldn't come on. Ch and wireless icons continuously flashing on the panel. So I put batteries back into the old Thermostat and heypresto the ch came back on. Also nest is also working. But I'm not sure both thermostats should be active.? If you agree what needs to be done in order for the boiler not to be firstly dependant on the old Thermostat before allowing CH? Many Thanks