Well, the replacement hard drive for my notebook arrived this morning from Amazon.co.uk (nice and fast, that was good!), and inside the larger-than-expected box (L 23cm, W 16cm, H 11cm) was a surprisingly small hard drive (roughly 10cm x 7.5cm x 1cm - Good God, these things have got a LOT smaller in thirty years!), sealed in a factory-issue Toshiba-stamped Anti-Static bag.
The new drive was successfully fitted (it was pitifully easy, one screw, prize off a plastic panel, carefully ground myself against the metalwork (static electricity kills modern electronics), and swap them out. Many orders of magnitude easier than when I worked in the IT game - at least someone's learned how to make things simple!)
The installer, running off a LiveUSB thumb drive, did the job with no problems; the new installation then took itself off to update everything in sight to current release levels, as expected.
All in all, a relatively easy and simple fix to conduct. Nice to know some things come along with no dramas attached!
One or two comments need to be added, however. The installer makes one massive partition; you really need three: One for the operating system, one for your data, and one for the swap file. For this, you really need a decent disk management tool, and there exists in Linux, one such excellent tool, called gparted. However, it's been over two decades since I played with partitions, and a LOT of standards and practices have changed in that time, so I left it to the Ubuntu installer to do its thing.
And got one partition, not three. Live and learn.
I'll know better next time (and there WILL be a next time, as I plan to replace this new hard drive in about a year, with a Solid State Drive, which are much better than conventional hard drives (or HDDs), as there are no moving parts in an SSD, they're on average three times quicker than an HDD, consume less power, don't get as hot, and are quieter as a result of all of this as well.
The downside at the moment is that SSDs are expensive in comparison to HDDs, and tend to have much lower capacity than HDDs. Hopefully, that will have changed a fair bit for the better by this time next year.
And that will give me sufficient time to bone up on current partitioning practices, so I can do a much better job of sorting out a new drive for the machine.
Still, at least it's done for now