David, I tried to buy a car with a heated rear window last year and took the hard top off to inspect further. If I remember correctly the n/s rear trim panel behind the door had a leather/tex flap of some sort near the seat belt with a wire connector of some sort and there was a switch behind the ashtray in the centre console. If it helps the car is now for sale with Howard Wise Motors, he can definately tell you, it's a pale blue car.
Neil