Ah ok - so likely they were already using channel name LongFast and slot 20 then as they were definitely 0 or empty I may as well revert them back. I haven't seen any other nodes show up on either of the meshtastic maps so its hard to be sure if there are any nearby or not, though I have seen some show up in my nodes list as seen direct & on lora so I assume there are some nearby.
But that was why I was trying to get the mqtt part to work to try to confirm I can pass messages ok - i'm using the msh/ANZ topic and I can see that on the mqtt server with messages flowing in so it does seem like I should see something.