I appear to be almost there with my setup. My main issue now is that unauthorised access results in a 404 rather than redirecting to the protected content page I created and referenced in the membership options page. I've set "Override 404 with protected content page" to Yes, although admittedly I only did this a while back. I don't have any caching plugins installed, so I'm assuming the change would take immediately assuming I did a forced refresh on the browser.
I've configured stranger settings to give access to a base tier which includes most of the site and protects 3 pages via negative rules. I have 3 levels, each with two associated subscriptions, each giving access to all free content and to one of the 3 pages above, again via negative rules. If logged in as admin I can access the pages without issue, but persons not logged in or logged in but without access privileges for the relevant page get a 404.
It's a single site install plugin v2,0.7, WP 3.2.1. I've been unable to find a solution by searching the forums.
Thanks for reading.