Illustrator Workspace and Toolbars not appearing

Hey all. I booted up Illustrator this morning [a W10 PC] to suddenly find that none of the toolbars or workspaces show up, just the artboard.
I can toggle each element separately [Layers etc] on from the menu above, but they do not remain with a fresh session, and trying to even switch to one of the default Workspaces [less my own] does nothing.

I’ve tried resetting to the default Preferences, as well as making sure I’ve not selected the Tab key on my keyboard somehow by mistake - but to no avail [of course].

Just wondered if there was anything else I could do before trying this Creative Cloud Cleaner tool for a clean installation? 

I’ve never had this particular problem in all my years with the program. And I’ve been on this latest public version since it went live, so weird how it just happened now.