I was going to try to find the factory seat elements and switches, but I decided that for 60 quid, I'd rather have brand new elements, with two heat settings instead.
The covers come off the seats quite easily, I was pleased to see that velco is used instead of those nasty 'hog rings' that are a pain to remove and get back on again.
I had to install the lower element back to front so the cut out would fit around the central velcro strip, but it works pretty well.
The rear elements went in with no problem.
Wiring was a snap as my Megane CC was pre-wired for seats, so it was easy to identify the wiring on the plug under the seats (unfortunately I didn't take a picture of that..)
One of the hardest parts of the job was actually removing the seats from the car as they are so flippin heavy and cumbersome to get out.