Mista2 solution worked:
Reinstalling the Outlook complication from the watch Apps Store seemed to fix the synch issue for me, it hooked right up. I don't know if this was complicated by the Outlook on my phone being pushed from our corporate management app, but I had tried reinstalling and updating the iPhone app too with no success or change on the watch.
The only other thing I did was edit my watch face to remove the complications from the display, as they still seemed to be stuck displaying the last synched data, even though the Outlook watch app had been removed.
So to fix my instance:
1: From iPhone Watch App, remove the Outlook complication and confirm removed from watch app list
2: Edit watch face to make sure no Outlook complications in use
3: Access the Watch App Store and download outlook from there
Now appearing to synch OK when Watch Outlook app launched.
I can now re-add the Outlook calendar and inbox complications to my watch face and they display the correct data. Though initially the complications again only showed last synched data from 4 days ago, until I opened the complication, then it updated.