Just to let you know that once I was confident enough that all I needed to do was to pull hard (er than I was!!) from the AC controls the headunit came out in seconds. I lost two of the clips down the back, but once I put the headunit back in its place and put the two screws that secure it to the dash it's just fine... and it'll be easier to pull out the next time! :-)
Just make sure that you do take those two screws out. They're at a really awkward place and you have to somehow get your head under the the AC controls (or thereabouts) to actually see them.
Finally I followed the wiring diagrams shown here:
http://www.hondafitjazz.com/audio.htm
and it works just fine. I think I'll add a pre-amp tho cos it sounds a bit weak and flat.
Another thing is that I had a few CD audio cables for PCs. The ones that connect the CD drive to the soundcard. It was great for the headunit's first 4 pins. I also found a similar cable for just 2 pins so with those two connectors I had covered all six pins. A little bit of soldering and heatshrink and in the end it looked quite professional (if I may say so myself!).
Perhaps someone will find this helpful.
T