Anyone have any experience with only drivers side seat heater not working… No light…
right side fine…electric seats work fine…Module??
What part? Seat need to come out?
I cannot recall which XK has the seat heater option… My XK120 definitely was not fitted with such… 
Obviously your mufflers are too well insulated then🥶
I’ll move this to the correct forum. And welcome Paul, this is an easy mistake to make and you are not the first and wont be the last.
I think the heater elements are in SERIES so you need to unplug each one and check for continuity. They are prone to open circuit and become inop.
The elements are located under the seat cover so some seat disassembly is required for replacement.
Could be the module. The circuit board copper traces are known failure points.
Remove the module to inspect the circuit board. (new plastic mount covers used to available fo
Is your clock working on the dash?