No idea why it wasn't working - downloaded all the latest drivers but my MacPro did not respond to the 802, even after many restarts and re-downloading of the drivers. So this is what I did:

Firewire 800 was working on Macbook with Yosemite.
Firewire 800 not working with High Sierra on MacPro.
Plugged into MacPro using USB to Thunderbolt from FF - started working.
Upgraded Macbook to High Sierra - unplugged USB connection and connected to Macbook by Firewire 800 - working (So no problem with High Sierra)
Connected again to MacPro using Firewire 800 to Thunderbolt - and it worked.

So no idea really what the problem was. Perhaps it just needed a kickstart using USB? Who knows.