Warwick,
Re your ASC problem. I have a 1995 540iLE (#50) that had the ASC warning light on all the time. In my case, it turned out there was a broken Bowden cable that runs from a servo motor driving the cruise control, to a butterfly valve in the air intake. The servo motor is located down behind the left headlight. There are 2 cables coming from there: one is a cruise control cable; the other is the one I am talking about. Once this cable was replaced, my ASC warning light went off, and now operates as it should. I am not saying this is your problem. But you might want to take a look anyway. I think the replacement cable cost about $USD25 + shipping from BMA Parts. It was more challenging to fit than I was capable of, so my friendly independent BMW mechanic did the work.
Just a thought.
Robert
1995 E34 540i Manual Limited Edition -- #50 out of 70 Australian RHD. Have owned 3 x E34 535i 5 speeds and E36 328i 5 speed (in the US), and a 1982 E28 528i, RHD Australian Euro-type 5 Speed.