Alas. I spoke too soon, the NVIDIA drivers have started misbehaving again.
I set up desktop extension so I could use the TV as well as my monitor. It all went fine. Then when I was done, I put it back into single desktop mode on my monitor. Then, and here’s the bit that shouldn’t happen.
I changed channel on the TV to the Playstation’s. This resulted in my desktop automatically adjusting to the previous extended desktop set-up, leaving me with a blank screen and not a even a taskbar to do anything with. Why does the computer switch to a device I’ve just switched off? Who knows. I expected a reset of the computer to give me a display again, but no, I just get a black screen. The log-in information is being sent to the device it switched to when I switched it off.