Whilst playing around with video settings I changed 'switchres' value to 1 which allowed Mame to run from desktop with
poor resolution in UI and 'in game'
Switched value back to 0 and Mame starts and runs perfectly from Win10 GUI to Full Screen Mame UI even after rebooting ...
That fact that there was no mame.ini file in any of my unzipped Mame directorys is also odd ?
# OSD FULL SCREEN OPTIONS