Took a chance and installed the new (ex demo) boiler switch this morning. It appears on the app as a thermometer, and interestingly, on the schedule ( in the app), the OFF times show as 17° and the ON time as 21° . Confusingly, figures of ( apparently random) actual temperature show on the app, even though I've not linked the switch to any thermostat, occasionally the actual temp just shows as two dashes --.
I can control (on/off) directly from the app by adjusting the temperature slider so all is good.
Thank you for your quick reply last night.