had a little crack at this again, the Mrs is bugging me to get “her” mirror back up and running.
So I’ve run sudo umount /dev/sda1
sudo umount /dev/sda2
Both drive folders from the mounted (old) SD disappeared from the home screen on the pi as expected.
then run, (and got)
sudo e2fsck -f -v /dev/sda2
e2fsck 1.46.2 (28-feb-2021)
rootfs: recovering journal
superblock needs_recovery flag is clear but journal has data.
Run journal anyway ? YES
e2fsck: unable to set superblock flags on rootfs
rootfs: *********** WARNING: filesytem still has errors *********