When I tried to upgrade to 13.10, it was appearing on the screen while preparing to update
Third party sources disabled
Some third party entries in your sources.list were disabled. You can re-enable them after the upgrade with the 'software-properties' tool or your package manager.
After that it was on:
W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_saucy_universe_source_Sources Hash Sum mismatch , E:Some index files failed to download. They have been ignored, or old ones used instead.