Ok, took a while, but that seemed to have worked for one spammer!
Having an interesting issue now ... most likely caused by me trying so many times to use the Spam cleaner (?), but my homepage is still riddled with threads by another spammer ... however there's no hyperlink on his name, nor does his name show up in searches via the front-end, or ACP??
Could the spam cleaner have gotten halfway through and deleted the user, but not cleaned up the threads? (the batch thread update also apparently finds now threads by this spammer, even though they're clearly visible in my forums.