OK so we're finally back flying. So I thought I'd update in case anyone searched for this and it may be useful.
So I ordered the 15cm frSky from amazon. The connector was massive, so I sourced a replacement from some place in Hong Kong. A couple of weeks later and here is a picture of socket, replacement antenna and too big antenna!
Still no joy with it working. So after a few hours of fiddling, upgrading betaflight, flashing etc, I noticed that if I pushed down on the connector (hard), I could get "telemetry gained", "telemetry lost" from the Q7. So after all that I think there was something wrong with the receiver board.
So I ordered another from UnmannedTech (thanks Alex).
So it was a bit of a nightmare trying to unsolder the 5 pads and the headers, in order to separate the F3 minicube.
Bit of solder sucking:
Bit of brute force:
I soldered back on easily (after all of that). And I can report ........... we're flying around the living room annoying the wife again
I now just need to find a successful way of determining low battery voltage.