You were right!
Selected to show file extentions then went through the import brushes again could now see the files with .afbrushes. extentions.
All files successfully installed and show in right side window even tried a few brushes.
Also had time to play with "affinity-photo-public-beta" and already can suggest some additional features and tweeks to some of your tools.
Will post my suggestions, when i have time, in the feature request section which im shore i noticed earlier.
Bye for now.
Edit. Thanks for extra info.
I remember a while back coming across a reference that the "unhide aspect is best left ticked/on" so you can more easily recodenise virus extentions and be able to deal with them.
So i will leave "unhide" on.