Thanks (again!), and for the comment. It still hurts though as I try to be absolutely as security aware as I am backup plan conscious, and something got past me. Grrrr!
Regarding encryption I have been using Memeo Backup for some time now but whilst I have elected to continue using it with the NAS I have likewise elected to continue using it without invoking the encryption option. My thinking here was that the benefit of being able to manually restore if the auto restore was ever needed but failed [the backup follows the same logical structure and is viewable (but must not be edited!) via Windows Explorer] outweighed the encryption benefit of a device on an internal network with strong firewall and which is unlikely to be stolen.
Perhaps time to have a rethink.
Regarding the RAID "reformat" I have successfully gone from RAID 1 to RAID 0, rebooted the NAS, and then gone back from RAID 0 to RAID 1. All is well and the free byte count is correct.
The next job?
To work out how the hell to remove (a) MioNet, (b) the Public Folder, and (c) the Download Folder without resorting to SSH and a hack. I have decided to live without MioNet and use web-hosted file sharing on demand instead and I don't need the two described folders that are a CIFS standard.