possibly another suggestion. Can pages output other formats besides epub? If you could save the book as an rtf file, for example, you could then use LibreOffice (or OpenOffice) with the
writer2xhtml extension to output a fairly decent epub that you could easily clean up in Sigil as necessary.
NB: writer2xhtml is a part of the writer2latex package at the above link.
All of the above software is free-as-in-speech, as far as I know.