How can I get past the blank purple screen on my Ubuntu 18.04 LTS system?

Wed Sep 4 05:48:18 UTC 2019

It does appear that it's a problem with the compatibility between a recent version of v18 LTS & the desktop PC's monitor, as I can get a remote desktop on a laptop, but the desktop PC display works with Win 7 (it's a dual boot) and the GUI on that display works until I log in.

It feels like something in a recent update has broken it, but I don't see any outcry on askubuntu.

I'm not sure what to try next.

Any more ideas folk? Escpecially ones to do with recent software updates around the GUI components?