have figured it out now...
created .htaccess with this in it:
place that in the folder that you are 'hiding'. This creates 'forbidden access'
Then create a 403 error and either point it to your 404 file or create a specific one for the 403
The folders are now 'invisible' (visitor just gets taken to the 404 or 403 page you create if they try to access the folders) but the files that are included in that folder can still be linked to (and subsequently downloaded if required)