Electric Underfloor Heating

Options
Is it possible to add an additional wired smart thermostat?
If so, I could replace the existing UFH Programmer with it and use it to switch a 240v mains relay.
I know there are questions re underfloor thermostats to limit the temp of the floor, but I have tiles so it should be ok.
It may take a bit of trial and error to determine how long the floor is heated to get it to a ‘safe’ temp.
There may also be an issue with the batteries in the thermostat not lasting long due to having to activate the relay coil.
Any comnents/ideas etc?