Got it figured, I did everything correctly except wait!
The Home Hub is on the ground floor and I'm on the top, with 5 other devices connected to the router. It was taking a minute or two to discover my pc, then a further minute each level of directory down.
I've rebooted the Home Hub and it has improved markedly, although the types of file that will stream over to the device are somewhat restricted; avi's play fine, mkv and mpeg will not play. Music seems fine. :)
Tried to send some video to my XBox but was unsuccessful, may not be enough bandwidth I guess...
Nexus 7 - July 2012
Lumia 920 - December 2012