ok, this is how i did it!
it is not for the faint hearted, but it looks alot more complicated than it actually is.
1st- remove the HU using the method in the first post
2nd- take the complete unit indoors and remove the trim panel from the radio cage (housing). 2 black screws.
now you should have the HU on its own and ready to be taken apart.
3rd-
remove the left and right mounting bracket, taking the 4 gold screws out and then the final black one (same for the opposite side)
4th
remove the front fascia from the rear of the unit, work from one side and release the clips gently using a flat blade screwdriver
5th
once the front fascia has been removed
you will need to take off the bottom panel to expose all of the boards and contacts
there are about 8 screws and some are mounted on the front and back of the unit.
once these screws are removed the lid should come off with a bit of prising from a flat blade screwdriver
6th
now you have access to the terminals and boards the rest is easy!!
all i did was use the cable from my tape adapter and solder that onto the terminals.
i used a continuity meter to test which ones were the left and right sides of the 3.5mm jack and to make sure there were no breaks.
once in, i tested end to end (from the soldered joint to the corresponding jack input.)
i then used the little notch to the right of the terminals to thread the cable through
reassemble the opposite way, i "pinched" the new cable via a between the lid and the main unit so that it would not go anywhere if pulled a bit.
i would advise that before you put all the trim back together and reassemble the car, you plug in all of the relevant plugs and test the newly installed cable with your MP3 player.
i have thread the cable all the way back into the armrest cubby but it was VERY tight on the cable length.
it does seem to be an easier method to soldering and cutting tracks on the PCB. well worth a go IMO!!
good luck
hope this helps!
Sparky