Steve,
I'm almost certain that a really decent kit was about £40 (eBay or Amazon - I forget where). The cost of wire, connectors and a 'piggyback fuse' is fairly negligible. The most expensive part (for me, at least) is the time to do the job!
I liked the SAAB seats a lot - very comfy, and the heating was superb and fairly intense when set on high - perfect for winter motoring with the roof down
. I've heard some other car makes are quite poor in comparison. I think Lexus was mentioned as being weak.
Either I'm going soft in my old age or have been spoiled by the SAAB seats but I really do like them, hence the thoughts of putting a heated seat kit into my 1970s MG. (Having driven it for some twenty years previously in only a WWII flying jacket and jeans!)
Although the Midget heater was fantastic, and with a tonneau fitted over the passenger side the heat stayed 'trapped' in the car under the tonneau, so your feet and legs were toasty, but the upright windscreen made it very draughty and bitterly cold around the back of your head and shoulders. The high collar of the sheepskin flying jacket was a revelation!
I'm now also thinking of fitting a kit into the 4x4 Jap scrap that I've just acquired -just for those cold mornings when going off to work. I might not have a SAAB any more, but it has changed a few perspectives and ideas in my motoring, so it has affectionately left a legacy
