Finally, sometimes I dislike CSS. It can be such a pain to work out why it's not causing an epub to display the way you think it should. Even after converting one into an ODF and then re-converting it to epub, it still wouldn't display right. Finally realised several of the styles were overriding the margins so paragraphs weren't spacing properly, amongst other things.

Sorted out now, cleared out all the spurious CSS, stylesheet is back to basics, and I can finally read #HaltingState