Thanks,
Just to report back and close this issue.
Dropping DBs, updating sources.xml and advancedsettings.xml did initiate a new databases to be imported into the mysql server.
However I was still seeing the error related to the Playlists path still pointing to a location on the old NAS.
I found a setting in GuiSettings.xml that contained the incorrect path which I reverted to the devault value as below
<playlistspath>special://profile/playlists/</playlistspath>
However to reboot it reverted to the old NAS path again.
Took the nuclear option over the weekend and flashed a fresh image of Libreelec on the SD-card.
Pity, I couldn't find where this value was coming from
I appreciate the tip which helped the troubleshooting process!