Ok - here's an update on this one...
As you see from my screencaps, one of the major discrepancies was in the notrades value (and when I posted this was WAY out across all my sites) - well, it's two days later now and somehow the notrades values are now correct in the network manager screen. On the one hand that is good (because they're correct) but on the other it's not so good (why was it wrong in the first place).
However, the productivity values are still different - but I think I know why. The site productivity seems to be calculated from the total IN and CLICKS in the bottom row - ok. In the network screen the CLICKS figure seems not to include the NOTCOUNTED amount from the site and the network prod figure is calculated using the INs and CLICKs on the network page.
From a site management perspective I would expect the network page to show me EXACTLY what I would see if I went to the site itself. I don't mind if NOTCOUNTED is in or out I expect the figures be consistent
Thanks