The final outcome...
Dear all,
Thank you for all your help. And special thanks to K1 for the piece that helped us solve the puzzle.
I had seen a floor stock car and been offered a price which I thought was ok. I have had seat warmers in previous models, I think it is huge fun to have the roof off in winter here, which is mild enough, but the warmers make it possible on even the coldest Sydney day. I counter offered that I would take the car if the put warmers in, knowing it was a couple of thousand AUD on the 996. What followed was very funny, as it appears no one in Oz had tried such a thing before. The final, official, answer from the factory was that it can be done. The dealer's preference was to swap the actual seats with another vehicle which had heaters, so as to do away with risk to upholstery. The fibre optic backbone and the PCM needs some work so it is ok with the additional equipment. The dealer absorbed the cost, which must mean the real cost isn't much more than the 996 cost which they confided they had thought was about what they were up for...and the result is a car that is exactly what I would have ordered! Very happy.