Not only that but it seems to insist on have 4 copies. Two small the same and two large the same. And they're low res too so most useless for me.

Does this stop it under Tools->Options?

Library Tab - Uncheck - Retrieve additional information from the Internet

Privacy Tab - Uncheck - Update music files by retrieving media info from the Internet

You can always do a global search for the files to get rid of them rather than having to restore from a backup.