ok, here's what I've found so far…
Shares appeared to be identified in the following file /usr/private/user_smb_conf/.overall_share
This file is called from /etc/samba/smb.conf.
I changed the .overall_share, as I wanted, by commenting out the Public & Download shares, & saved. Restared Samba - shares had vanished!!
But..I restarted the drive & the shares had re-appeared & the changes I had made to .overall_share had been overwritten. There is something overwriting the file - but I don't have enough know, to know how to find out what…
What I have done as a "work around" - I have created a ".overall_share_new" file - where I make my changes & I've changed the line in the smb.conf to call this file instead of the original. MyBook has been rebooted & only the shares I want are shown :-)
Not the best solution, as if I want to create new shares, I'll have to do so manually via ssh - but it works…
If anyone can help identify what/ where the overwritting of the .overall_share takes place, please let me (& anyone else who wants to know) know.
Hope this will help some people.