Hi Roman,
Thank you for your response & apologies for the delayed reply.
I tried removing the 'Media libraries folder' setting and uploaded a new file (which went to the default directory on the server) but the permalink was still returning a 404.
The paths being generated via the Media library picker on a doc type property & the preview URL in the media libraries are in the following format '/getmedia/4554367f-adea-459d-85b7-4eb5dba21af1/test'.
I believe enabling extension-less URL's will be the cause of the issue but i cannot a resolution.
Thanks
Anthony