... and now all of a sudden it has started working. I'll push on with the rest of the stuff I need to do to get a full production server up and running. I'll need to set up a VM to have a play to see if I can replicate this.
Brian, it was a different card I put in this time. It was doing exactly the same thing, but suddenly started working. The Internet test from the admin console still doesn't work, but I have Internet access from a PC using SME as its gateway.