Thanks everyone for your input.
Antenna's site would not allow us to seemlessly move our current data into it and merging into another forum would potentially be possible but one would need to buy,find or build tools to do so. I make my living doing integrations similar to that, but at the moment I would not hazard a guess on how difficult it would be.
A full migration to a new domain as it is (with me donating my software license) would probably be the least problematic. (And as I have said before people playing a 27 year old game may not be the most accepting of change
)
There is now real rush on this so the Mods and I are working carefully to plan the best next steps forward.