And so I reverted.
Back to Pear Linux 7 that is.
Mint KDE worked, mostly, except for DVD playback - though it wasn't opening DVDs at all until the region code on the drive had been set - which was too much to expect of an older machine running a demanding modern operating system. I really like the way that when opening an audio CD, KDE's file manager offers the audio for download to the hard drive in every format for which the machine has codecs loaded.
But it was sluggish and the machine ran warm all the time, even when idling, which was going to kill battery life quickly. Less good was the lack of hard drive encryption, and if I am to take personal data with me then I really don't want to risk it falling into anyone else's hands.
I'd been discussing the issue of getting 'non-free' codecs onto pear with one of the guys on the forum, and it turned out the problem the previous day was my failure to direct the machine properly. So a quick reinstall, a few minutes on the command line and the install of a bunch of updates and voila, DVD playback!
Security is better with pear too, and to access the machine a hard drive decryption password is required as well as a (different) user password to access both the desktop and any control functions. A real time battery life check gave a genuine 2 hours including some thrashing of the hard drive when too many programs were open at once while installing updates. Audio quality through some cheap Radiopaq headphones (£1.99 at ebuyer) is also more than fair, and Dire Straits Lady Writer was clear, detailed and involving.
Looks like that's pretty much sorted then. Just need to set up email accounts and it should be ready.