Thank you all for your replies and your help. My system is now working as I wish. For some reason as yet unknown to me. The Screen Configuration tool in GUI has changed its available resolutions. It now has 1920 x 1080 which it did not have before I started this thread. I obviously did something with xrandr or in /boot/config.txt to cause this change. It probably changed during a re-boot as I was very careful to monitor the effect of each change. I also only changed one thing at a time. Heck, I'm a retired IT guy. Computers do what I tell 'em. Noth this time though.

Thanks again for all your help. Much appreciated.

Clear skies to all.
Pete

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