Anonymous FTP Permissions

I’ve configured anon FTP and set up a few directories in the root but I can’t write to the directories using my FTP client. I’ve given the directories the correct permissions to upload etc but I just get permission denied whilst trying to upload. Is there another account I must use to upload files or should the “anonymous” username be able to upload stuff if the given permissions are set correctly? I’ve got the permissions set right but still no joy. My new unique IP resolves as my site name so it’s not that that’s the problem - anyone any ideas? Am I missing something?
Kate c