Hi,
Just fitted heated rears to mine, you need the complete set of rears - rear bench base and 2 x heated backs.
Plug lives under seat all ready to go, there will be a plug also for the auto levelling rear suspension, your loom that'll come with the seats will plug into only 1 of these 2 plugs.
Route the wiring and 2 x relays inside the metal tunnel box section under where the bench goes, and feed the wire up a little hole in the middle of the car next to the transmission tunnel, this'll then marry up with the location of the 2 x heated base plugs. 2 more plugs connect to the heated backs.
Brackets live behind the carpet held on with black clips, unbolt those on your old seats, the same will apply when you attach the new heated replacements, fitting is the same as removal as they say.
Lastly, remove your old centre console panel, to reveal your plugs so as to connect to your new switches on the replacement panel, reattach your cigarette lighter wires.
Plug and play, it'll work straight away, no need for fuses.
Hope this helps
Dean