Thanks for your response. I finally got this sorted last night. After looking at lots of forums and (often misleading) suggestions as to how to enter a folder pathway on a Naim Uniti Core, I finally found one that worked. In my case I entered the following pathways (where ****** represents the six digits in the name of the Uniti Core) -
smb://UNITICORE******/Music
smb://UNITICORE******/Downloads
Once these pathways were entered the Roon Nucleus immediately started to scan the music folders. By today all my music on the Uniti Core had been scanned and is playable on my Naim NDX2 using the Roon Remote App.
After faffing about for several days before stumbling on a solution I must say I think both Roon and Naim could make this a lot clearer.
Thanks again for taking an interest.