Owning multiple Facebook pages connected to the same organisation

Please can someone unravel my problem. I run a social enterprise which has a core facebook page plus several pages which reflect regional activity. I own and manage the core organisation page and also own the 2 regional pages. I have registered the core page and one of the regional pages under the same email address, whilst the second regional page is run from a different email.
My problem is this - I want to post as the core organisation and comment on the regional page activity which is managed by regional admins. However, this appears to be impossible - whether on the regional page with the same email address or the regional page with a different one. Surely there must be other organisations with a parent page and multiple regional pages all owned by the same person. Any insight, advice or suggestions would be gratefully received. Thank you