Funny how just posting a question has me finding the answer myself a short while later.
IT'S WORKING !!! :-)))
I created an
outlook.com email address and used that to log into the Outlook.com app on the S8. Now the calendars all sync perfectly. Works with web browser online versions as well as Windows 10's built in calendar app.
All the trouble I was having appears to have been caused by associating a Gmail email address with the Outlook account. Glad I got it working this year.
Happy New Year all 