Many thanks everyone.
Reflashed the 8500 with 5.4.003 and the time problem was resolved.
Unplugged and re-plugged the powerline adapter and ethernet was working again.
I also took the opportunity to mount the power and aerial gangs on the wall to make access easier as the TV cabinet weighs about a quarter of a tonne (well, it feels like it) and takes 2 to shift it when changes are required!