Okay so after much investigation by myself and a few not so helpful chats with support I've found out the following for anybody that would like to know.
Some time over the last few months after being bumped up from 20GB to 100GB, it looks like Document Cloud files were included in the quota.
Once the old stored sent files were deleted my storage came back down to 12%. There seems to be another 2-3GB in the mix there that I can only assume are either libraries or mobile creations files.
I appreciate that the CC sync team are busy moving everything over to the new system, looks like it will be a well integrated unit when complete. Although some from of communication about the change in storage quotas, and what counts towards it, would have been appreciated.
Would love to have a very basic break down of where my online storage is going as per the iCloud storage meter. This would alleviate a lot of guess work and give the user the feedback needed to make decisions around what to store.