Thanks. Out of technical curiosity I'll continue to fettle with Outlook 2016. The navigation panel seems to pick up the correct number of unread emails etc but the preview screen just sulks. It's backed up but only via an image of the pre Wndows 10 c drive. I'll set up Thunderbird first then get back to it. I tried renaming the ost file as per most Internet advice without joy. Pointing 16 at a different data file location sounds worth a go.
Cheers all.