Obviously being the fussy purist that I am, this just would not do. So I set about rectifying the situation. I figured I would do a write-up detailing how easy it is so that others may benefit from my efforts.
The first thing I did was some research with BMW. I discovered that there is an accessory panel in the glove-box with a power outlet for a radio. OK I thought now to start looking for an ISO terminated lead. After around oh lets say 2 hours of mindless Internet searching (no porn honest guv) I found that Blaupunkt sell them on their website. Here's a link:-
http://www.bluespot.co.uk/install/show_model.asp?id=23
The one you need for the E30 is Part reference: PC2-25-4 and its £9.99 Bargain!
OK, to do this properly you are going to need the following things.
One of the above leads.
Male and female bullet connectors, or spades it dosen't actually matter as long as they are insulated.
A crimping tool (available at halfords and relatively cheap).
Screwdrivers.
A basic understanding of wiring.
Patience, fags and beer is always good.
So here is the first picture showing the abortion of wiring kindly left for me by previous owners!

First thing to do is remove your stereo (if fitted).
Then open the glove-box and release the two support straps. These are held in by two plastic pegs that just push out. You can do this with your fingers.
Then if you look to the left and up you will see a white box with some wires going in to it. Depending on how your car was sent out from the dealers it may have a plug already located for the radio. If so pull it out and junk it.
Now take the new loom that looks like this

And feed it through the stereo aperture and send it off to the left towards the accessory board. Remove the plastic trim at the top of the glove-box for better access. When you get there plug it in in to the board. You can't get it wrong because it only goes in one slot!
This is the accessory board with the loom installed.

Now you need to remove all the dodgy wiring (if any). Mine was relatively easy as it was wired in to the hazard switch.
It should then look like this with just speaker wires and the aerial.

You then need to do a bit of modifying of your new loom. For some reason on mine the orange and yellow wires needed reversing. Just cut the wires and connect yellow to orange and vise versa.
Then cut the thin black plastic plug off and connect bullets to each wire. Connect the opposite bullets to your speaker cables and connect them up. Pay attention to front/rear left/right etc and positive and negative.
Bullets on the speaker wires.

Then pull everything through so it all looks neat and tidy like this.

That's it! Easy or what!! If you check the clock you'll see that this whole job took me an hour and ten minutes. Mind you I did have two tea and fag breaks!
Heres the stereo all plumbed in neat and tidy!













