The light comes on on the control switch. Neither the seat base nor seat back heaters work on the driver's seat but both work on the passenger seat. Not sure whether this is relevant but the interior lights were left on and ran the battery completely flat. The seat memories had disappeared but my daughter thinks the seat heating was off before the battery went flat (I am suspicious about coincidences though). I restarted the car by connecting a moderately discharged spare car battery in parallel with the flat one while it was in the car. All seems good now with the battery, but could something have gone wrong with the seat heater as a result of the flattening or recharging of the battery?
I've looked at that diagram a few times Colin, but it looks too simplistic compared to what's actually under the seat. One would imagine that it would be easy to simply unplug both 'seat heater controls' and swap them over, but I can't identify them in real life.
Mike