Will: Thank you for your time and patience. They are child portals of the same domain as Site ID 0. ie:
https://AppDomain.Site0.co.uk and https://AppDomain.site0.co.uk/Site1
Have we misunderstood something, does this not allow separation of logins and folder security on each site? As I say the page edit permissions work as expected, it's just when a user login attempts an upload that doesn't work.