Hello Dave
Are you sure you actually want to give site-wide access to the Guest account ?
Because what are you seeing is exactly what I would expect that setting will do - give Guests access to everything on the site - site wide !
For providing Guest access to resources (e.g. not having to Login) I would either create a Course which is set to allow Guest access, and then Guests can access everything in there within issue, or maybe add Resources (e.g. Pages) to the Front Page menu, but hidden, and provide direct links to these ?
Stuart