Originally Posted by jackie_w
Another option for your consideration. For simple EPUB tweaking, I find the little free utility discussed/offered on the Atlantis WP blog
quite useful. You can tweak most of the epub constituent parts, including toc.ncx, in-situ using your favourite text editor, without destroying anything.
This is a seriously helpful utility. It lets me use VIM's regular expressions to fix no end of formatting problems without any unpleasant side effects. Thank you for pointing it out.