This seems to be directly an XFCE problem, as I tried MacPup and it was exactly the same - would not configure up either ethernet or wireless. Whereas an Live install of PCLinuxOS with KDE worked flawlessly. Much is the pity as XFCE is so much less resource intensive.
But surprises me that ethernet cant be used, as thats always been straightforward on my pcs. I have tried 3 different PC with XFCE installs and they all fail with networking.
Tried it again, and it works. Seems flakey as I didnt do anything different.