I expect to be doing major upgrades on the hosting server for this site during the morning (UK time) of Sunday 24 February. Do not be surprised if it is unavailable then. I will post again when the work is complete.
This work has now been completed.
Thank you. That took less time than I was braced for.
This was the tricky one of the three machines I was working on, necessitating a rescue login and grub reinstallation through a chroot.
Good work getting it done quickly!