So hog tied all back together and reassembled.
Try and get round hog ties. The type i bought start out like a staple and fold to be triangular, with sharp corners at wire ends.
Some places i placed some plastic sheet from bottle of bleach to stop hogs shorting to the mat power strips.

Then decided to clean the kansas beige seat with bleach of all things and a small nail brush.
Just didn't realise how dirty seat was.

Then finish off with Autoglym leather protector.
Seat now looks as new as passenger seat that never get's used

Wiring was easiest to run to the forward cig. socket. I removed it and used it's power lines, also fitted volt meter in skts. place.

So all works great. Quite a challenge to test as car sat in minus temperatures.
But 10 minute drive seat was toasty, even with heavy coat on, back warmed up, i had to switch to the lower power setting.
I like to thank Tim, wouldn't have bothered without seeing his tutorial first.
How mean of BMW not to fit as standard.