Update on the updates...
The monthly update process eventually finished at 14:30 yesterday afternoon. After all the additional steps I had to make, and a system backup, it was 19:00 that I kicked off the final stage.
Got in work at 7:15 this morning... it's still running, and is likely to finish around 11:00.
This, of course, affects all system users, and is also a complete pain in the backside.