Thanks for explanation on system restore - I thought it did drivers - especially as it showed a restore point for the 'Driver Boost start'
An update on this issue -
Rolled back driver - no change
Tried to find correct driver on Nvidia site but it keeps failing as it wants Java installed and none of the W10 browser will work - even though I run Java installer - get same request to install Java.
Used W10 'find driver' - it updated - no change
Samsung do not list a W10 driver for the monitor on their site - W10 'find driver' can't find one.
Left PC overnight and today booted up and all back to normal
The NVidia control panel shows resolution back to 1920 x 1080 and all the other resolutions in place ... it also shows...