Yeah, I've used all of those options in the past, so I know what I was going to keep/lose. Irrelevant now that I've got the user account working properly again with NavyLCDR's tips (thanks again).

Side note: when I tried to turn File History back on, it wouldn't let me select the internal drive. Some searching later and I find out that MS have quietly changed File History to require an external drive, and are replacing it entirely at some undefined time in the future. I'm not currently sure if it does what I want of it now, or whether the new system will do what I want later, but that's a topic for another thread.