Seat Heating

I recently bought a '90 740 and have discovered that a previous owner has trashed the seatbelt reminder wiring and the heated seat wiring. I have sorted the seatbelt wiring and am now turning my attention to the seat heating - God knows why cos its 80 degrees here in the UK at the moment!.

I am aware that there are 2 versions of seat heating and I think previous owners have changed the wiring. To cut a long story short I want to go with the enhanced version!. I have the switches which switch to 2 positions but am not totally sure what occurs in each position. Also I have a cone shaped spring in each seat with some sort of thermostat in it? Is this what it is - none of my wiring seems to want to connect to this - is that correct.

Any help would be greatly appreciated, especially if someone wants to draw me a basic wiring diagram and email it to me:) I am OK with the wiring until it disappears under the seat.