@Herr Kaleu I'm also in the camp of space before a hyphen.
@Lone Raven has a preference for without, but to me it looks odd. In any case, there are definitely many priorities above this and they should be the main area of focus. I know it gets frustrating manually adjusting the file names, but that's just what we have to do. If you have a lot of titles to change (such as if it's multiple episodes of multiple seasons of a series with a colon in the name; e.g. "Colons and File Names: The Origin Story As Told By
@DQ"), then your best solution is to run a batch script that can replace the original string (without space before hyphen) with a new string (with space before hyphen).