Well after much playing around trying to get this working over the internet I finally succeeded. I used two computers to test it over the net myself, one through a router+broadband and the other one through a modem dial up connection. I took my laptop off the lan so there would be no confusion and after much playing around I finally got it working.
I found that the following ports should be open to allow it to work.
47624 udp
47624 tcp
2300 tcp
2350 udp
I needed to set 47624 manually, it's used for the initial connection and 2300 and 2350 open automatically after connection but I suppose I could have opened them manually too.
I couldn't get my router to work using port forwarding so I disabled upnp and set a dmz and all worked fine.
On the modem connection when hosting I went into network connections, clicked into properties of the connection, then advanced and settings for the windows firewall. Then I added both 42764 ports using the internet ip aswell.
So it all seems to be working, hopefully others can join in now. I have a server running at the moment and will leave it up for a while. It does seem to take a short while for the program to settle in and network smoothly but it does and I was using a 56k on one end so it could have slowed it a bit. Anyways now I can concentrate a bit more on optimizing the multiplayer code.
There are some minor network bugs I came accross while testing so I will upload a new version of the server and client later. The current files should still work ok though.