Electric under floor heating stopped working

First try to see if can be fixed easily. Does the thermostat have batteries that may need replacement? Does the thermostat have a way to reset. There are secret ways to reset or pair devices that don't come with instructions, fortunately the information can be found online for your particular model. Connections might be lose.The thermostat could be broken and is best replaced. The cost would depend on the model could be anything from £20to £200 plus call out charge for electrician. In the unlikely event of a worst case scenario the fault could be difficult to access without picking up the floor and would be an expensive job.