Somewhere in the config of either Sharepoint or TFS it's referencing the server name instead of the FQDN so after iVS has downloaded the 3.6 mb config file it tries to connect to the server name instead of the fqdn. It's either the config or the fqdn is being forwarded to the server name name.
The TFS server isn't on a domain and we connect over the internet to the site in Guernsey.