Thanks for that Stitch.
I looked around for these mounts some time ago and could only find the mounts for ground troop helmets. Quick search now has found what I wanted, fairly newly released.
TeeS
Actually, disregard the above, the release I found was from 2011 and is the one I had previously seen, the wording says
GoPro’s NVG Mount Makes it Easy to Attach a GoPro Camera to any Military or Civil Service Helmet Outfitted with a Night Vision Goggle Mounting
but it doesn't seem to be compatible with the FENS system which is what I am after. TeeS