al78, many people just use their thermostat as an on off switch - so it's their choice whether the heating switches on or off in the 'summer', not the thermostat. I just turn mine up to 18C when I want to turn it on, simple really....
I don't get that. I just set mine to 15C and let it come on when the temperature drops below that, since apart from using the radiators to dry laundry in the autumn/winter/early spring, that is the only time I want the heating on. If you are using it as an on/off switch what is the point in having a thermostat in the first place?
I've got Hive, so have just clicked it to off on my phone, but it depends how easy it is to fiddle with your heating. Sometimes using the thermostat as an on/off is the easiest way.
I am of the view that each to their own, so I don't need to get it. It is whatever people feel is simplest and more convenient for them. 15 degrees is low, especially for older people or those who are not so mobile for any reason. The recommend minimum is 18 for them to avoid slow chilling of their bodies which exacerbates aches and pains. Some days and nights recently would have not been comfortable without some additional heat.