Private Closed groups visible to non-authenticated users

Hi,
Please forgive me if I've posted to the wrong place etc etc, this is my first request.
I've set up a site which has organic groups. I need to make groups private but despite setting groups to closed/private/unlisted, an authenticated user/non-member can still access content.

Can anyone give me any clues as to how to make them hidden to non-authenticated, non-permissioned users? Or point me in the direction of some docs, FAQs or help? Ideally I want OG subscriptions to work with my groups but that doesnt work either and the help/configuration documentation is, minimal to say the least.

Like, I said, I is a newbie here and fairly new to Drupal, but an experienced developer. I just need a pointer or two.

Thanks,