Hi @neil,
I think all of the details you're looking for are already available in the Settings > Permissions > Topics section of your control panel:
/cp/permissions/topics
That page gives you a breakdown of all categories and forums, along with their permissions. It's not exactly the format you're describing, but it contains all of the info you're looking for.
Note that it's a single page with all of your forums listed, so if you have a large number of forums, you'll have to be patient for the page to load.
Hope that helps!
Brian