I've tried setting up a server on a spare machine, but so far can't get it to work. When I try to connect to it I receive a message saying something along the lines of "Server using different code version". (I can't recall the precise wording, and I've unistalled it now.)

I was connecting via the "join specific game" option since the server wasn't showing on the public list - but I know this is just an issue with opening the right port - surely this wouldn't have cause the above problem.

I've tried installing the main game files, the patch, then the dedicated server files, and also in the order: game; dedicated server files; patch.

Can anyone suggest a solution please?

Are you running the Dedicated server version U?
If you're not, and your game is patched to version U, you will get the "different code" message.
Also, make sure the server is running S2 if you are trying to join an S2 server.

Basically it means what it says. If you've got dedicated version U, and are connecting with an incompatible version, then you'll get this error. Make sure your LFS client installation, and the dedicated server are the same.

It also sounds like you've put the dedicated server in the same directory as the game - this is a bit of a no-no - trying to keep them separate is good.

Be aware, you don't have to use the dedicated server, if you dont' want to. You can host from the full LFS client.