Hi
The Hi-Low switch is a set back switch which allows the setting on the thermostat to be set back by 5° ie if stat is indicating 20° it will set the new on temp at 15° and this would be the same for all the thermostats in the property.
Regardless of the individual setting of each thermostat...
Most ceiling heating mats can be tested using a Ohm meter 0-100 range for larger rooms & 0-1000 range for smaller rooms (bath room size).
The Thermostats can be replaced using any suitable air measuring stat with the ability to handle loads of up to 16Amps.If the stat has a set back facility...
