Being charged for 1GB of space on my subscription

The document manager is found by going to Account Settings >> Tools >> Document Manager (more detailed instructions can be found here). You can download an archive from there too if you want to view the files in more detail (such as size for example).

These files aren’t automatically backed up to Dropbox, only your account data such as invoices, clients and suppliers are backed up here. However the archive option above can produce this if you wish.