Flashed my UK '3' S9 with the firmware linked in the first post (SM-G960F (single SIM) )
All appeared to work fine
But now I have the dreaded 'no entry' sign rather than mobile network bars.
Doesn't even seem to know the sim is in.
Tried reflashing again.
Tried resetting mobile network
I have fixed the issue now by following this tutorial and downloading an alternative Firmware version.
https://www.youtube.com/watch?v=SVhR0E9ACnY&t=155s
Would be interested to know if the firmware linked in the first post is meant for UK, because it did not seem to work for me.