Thank you so much for your help! That was just the ticket I needed, and stupidly, I should have realised that myself. After doing that it was booting up into emergency mode. It wouldn't recognize my root password, so I switched back to SD system mount, rebooted, mounted the system on SSD, chroot, changed root pass. Then noticed that fstab on the SSD was trying to mount /media/mmcboot with a UUID which I'm not sure what that was, presumably my old SD. Put the UUID from the current SD card fstab list into the SSD fstab as /media/mmcboot and rebooted and voila! I'm back in business, all services ticking along.
Simon Porter got a reaction from Igor in Fresh SD card - existing SATA