I hadn't even noticed the 'clean up versions' option, so thanks for the heads up. But I have just run it and selected all but the latest one - and I'm sorry to say it failed to delete all but the latest one of files like MSNBC News (2015_07_26 14_23_39 UTC) in my Favourites :-( So I have now turned File History OFF and will rely on my synced backups to USB hard drives instead.
But it is diabolical that this problem has been around since File History started and that so many people have reported issues with duplicates - YET MICROSOFT HAS STILL NOT FIXED IT!!!!!