Parrot, send me a PM with your email address, a few years ago when a lot of the original Boxster websites that pioneered some of these hacks started to go down as people sold their cars, I downloaded ever DIY, picture, etc I could find (about 6GB's). I have a folder with heated seat info, it's a bit confusing to sort through, but it's all there.
Also, out of curiosity are you doing the OEM heated seat install or are you using an aftermarket kit. If you have found a way to use an aftermarket heated seat kit with the OEM heated seat switches I would love to know how.