OK, so I downloaded the "Add To Server" plugin and added all my 100MB files to the media library.
I set up the membership plug-in to use an obfuscated download link...
I went to my post page and used the URL
when I go to the site page I get the above URL for the file, (all good so far)
I click on the file and get:
Fatal error: Call to a member function has_level_rule() on a non-object in /home/channelr/public_html/wp-content/plugins/membership/membershipincludes/classes/membershippublic.php on line 318