It seems I picked the wrong time to do a fresh install!
I fresh installed a recent MX-18.3 snapshot (built on a non nvidia machine without nvidia drivers),
The install went flawlessly of course, so I then installed Steam followed by the nvidia drivers (via the installer in the menu).
Everything seemed pukka, so I went ahead and brought my games down and tested them all on the new install with great success.
Upon rebooting this morning I find I can get to the login screen and enter my user name and password which gives me just the grey login wallpaper and a mouse cursor, from where:
Alt + Backspace doesn't take me to a command line,
F4 invokes a drop-down terminal which is invisible (the cursor changes to the text pipe when at the top of the screen).
Alt +F1 doesn't take me to a prompt.
I note the 4.19 bug that is affecting nvidia driver users here:
https://mxlinux.org/blog/our-recent-kernel-problem/ so i tried the 'add '3' at the end of the linux line' part to no effect unfortunately. No command prompt.
I also cannot opt to boot with another kernel as 4.19 appears to be the only one available.
I'm not sure what to do about this. My knee-jerk reaction is to slap on a new install of something else instead, but I'm certain this problem has an easy fix, as others with similar issues recently have found. I just don't know what that may be?