I desoldered the antenna and removed the excess blobs, and just tac-soldered it back down.
It locks reliably using usb and ublox u-centre, but switching to the Omega2+ and putting it in exactly the same position it can "see" 2-6 satellites (varies widely) and never locks position.
A previous post said the GPS expansion on an original Omega never locked and it was put down to interference from the omega and dock itself. I'm beginning to think this is still true on the Omega2. Moving the antenna away from the omega makes it work