Just spent the last 3 hours re-installing my head unit!
I took the dash apart again and removed everything. I then bared a bit of wire on the thin wire that connects to the cig lighter (12V switched after testing it with a multimeter) and wrapped my orange Alpine wire round it. I then plugged in the standard Autoleads wiring harness and found a switched live in the fuse box with the multimeter. I connected my switched cable from the Autoleads harness into the fuse hole, turned on the ignition and hey presto! Turned the lights on... and the stereo dims

I then realised that the farka aerial adapter I had bought had the wrong connection for my stereo, so had to travel to Halfords with my dash in pieces! I made sure I didnt disconnect the airbag light though. When I returned I ran the cables properly and soldered the orange illumination lead in place. I put a spade connector on the stereo switched one and put it into its fuse hole.
I then re-assembled the dash carefully... and tested it all again!
The stereo works exactly the same as with the Canbus, apart from the wiring is a little more complicated! Once thing I did notice on my trip to Halfords... and have noticed since I installed the Canbus which seems a bit weird: normally when you drive down hill or something with your foot off the accelerator, the MPG in the MFD displays a couple of dashes, but with the Canbus installed, it goes up and up to ridiculous numbers! When going to Halfords I didnt have the Canbus adapter fitted - and it just went back to dashes!
Anyway - I now have a spare Canbus if anyones interested?! It cost me £76.50 including delivery... and has only been used for 2 days! I'll let it go for £55 including delivery.
Now I'm away out for a drive to play with the stereo... and once it gets dark I can see if one of the 3 dimmer settings matches the aircon display!