@height8 I researched as much as I could (so I thought) about such things vanishing & discovered that if I retained my iTunes Match subscription as well as subscribing to Apple Music, I would retain control of my collection. That plus several local backups including on an 80 GB iPod Classic.
Turns out if I'd researched a little further at my ISP end, I'd have found that they offered a free 12-mnth subscription to Apple Music.