My interest in this has transferred over to my current car, a Jaguar S Type.
The big advantage with the Jaguar, I'm discovering, is that the wiring loom is standard throughout the spec range.
Today I retro-fitted top of the range, 16 function memory seats ( the headrests are even motorised and linked to memory) with 3 heat setting heated seat pads.
They were quite simply plug and play, the whole job, including the rear seats as well taking me less than an hour
No setting up, no wiring needed. That's the way to do it