This is resolved, so just a follow up in case it helps others....
The problem eventually spread to my other devices that connect to external resources: my Beyonwiz wouldn't do a time sync or connect to IceTV, my DVD player and TV couldn't connect to check firmware updates. Yet they all tested ok for network and internet connectivity, on both wifi and cabled. My laptop and i-devices all worked ok.
So after factory resetting the router, 2 x Skippas and meshed wifi, I eventually rang my ISP, TPG, for any suggestions. They advised it was a problem with their DNS and had me change the DNS defaults on the router. Problem immediately fixed at 8:00pm, after a full day of hair-pulling and angst.
So my gut-feel that it was internet related was right - it just wasn't at the IceTV end.
MD: Thanks for the help. The Skippa is still going strong.
