I can't believe after all this time it was the wrong cable that was causing the problems.
Andy (Gothic Rebel) thank you so much for actually having a solution that works!
Plugged the new retrofit loom in this morning, split the microphone cable away from the main loom (i didn't fancy splitting the cable and rejoining it with other cable) then retaped with amalgamation tape tested connection before i put it all back in place in the car and its now its fully working .
Only downside now is that i have a spare cable for a mk2 that i don't need, with both mic and audio patch cables and a sliced finger when cutting the tape!
- GothicRebel likes this