"User's $HOME/.dmrc file is being ignored. This prevents the default sessin and language from being saved. File should be owned by user and have 644 permissions. User's $HOME directory must be owned by user and not writable by other users."
I could login in OK, but something was clearly wrong and needed fixing. Change my name to your user name. Here's how to fix it:
(If you get permission errors when trying this then drop out of the GUI and into recovery mode. This can be done by pressing Esc on the grub screen and selecting the latest recovery version)
I'm not sure precisely why this error message started appearing, but it had something to do with the way I installed the latest wine. I did via command line and not by the package manager.