The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
Ah, thank you all for the help, it all appears to be running ok now. I incorrectly assumed that mod was essential and running without it was vanilla FA - I have no idea how it ended up in the mods list.
I will remove the mod so that I do not accidentally run with it!
