The very nice customer services person at Cobra supplied a wiring diagram, so for future reference, I'll answer my own question:
1 yellow key, 2 blue ground, 3 red +5v, 4 balck shield, 5 white mic, 6 green speak
the mic is susceptable to water ingress so I remove it between trips, the supplied 6 pin connector isn't up to this so I replaced it with a 6 pin mic plug off ebay, £3, and fanny is your dads sister.
If anyone knows how to lock the channel on the F55, to stop it wandering when you grab the mic, my life would be tickety-boo
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