Ok. issue is sorted.
I think the problem was related to the following:-
USING SERVER LAUNCHER
Console was giving me an error about not having the map CNC-Walls_Flying, so it said it would load default map instead.
I tried to change the map it loaded through config's and didn't manage to get it to work; watched the console and it still tried to load CNC-Walls_Flying and then went to default map.
The issue this seemed to cause is that I was stuck in the lobby, with one client stating Match was about to start in 4 seconds, but some different text (something about game tips or keys, I forget) on the second client. Could see both clients names in the lobby, and definitely in the same server.
USING BAT FILE
Used limsup's guide, loading up through a batch file, bit easier, and worked first time.
Not sure what I was doing wrong using the first method, but happy with how it's working now using a batch file.
Worth noting, my friend had this same issue, which is why he asked me to look into it.
Thanks for everyones speedy responses and help.