I still haven't resolved this .... for now I'm using only my calendar on my iPhone and iPad as these are syncing ok.
The problem seems to have started since I upgraded my iCloud storage - the iCloud calendar will sync but I don't like the platform as it is not a easy to view on my laptop as the outlook calendar (which also has a lot more features ....)
I suspect I'm not sitting this because I have limited technical knowledge but even my web designer who was a Microsoft engineer is struggling to find a fix for me .....
So unless someone can find the definitive - easy to follow solution, I'm sticking with my iPhone for now ....