Perch create page permissions error on live site

Hi there,

Currently using TSO host for a live perch website and I've not needed to create a page until now as I developed it all locally and just imported the DB. I am getting an error when trying to create a page:

Folder is not writable: /public_html/
Setting alert: Folder is not writable: /public_html/ (alert)
Setting alert: Sorry, that page could not be created. (alert)

I've spoke to the hosts and they can't understand why it's not writable as permissions according to them are correct. I can upload assets and everything in the diganostics looks ok in terms of being writable. Is there a chance there is something I am able to try to further diganose the problem? The strange thing about it is that I've got other clients running Perch on this particular host without issue and I can't see any difference in the setup.