Finally got around to trying to sort this out. After 1 1/2 hours net result is that I don't think I've sorted it. I swapped the leads. Although, managed to swap red and orange instead of yellow and orange. That was a panic moment when I couldn't get it working at all! I've also snapped one side of the bottom part of the fascia which is a tad annoying.

All wired up and still behaving the same. Oh well, it doesn't actually cause me any probs so will see how I get on with it.

BUT - I may, MAY, have sorted out the radio. Not sure if the wire was getting pinched or something but getting more stations now. The true test will be to take it out for a run and see if I lose reception along the A6.