After some googling I found that a fair few people have been having the same problem as me, only in FireFox though, every other browser is fine.  The problem was the CSS I was using:

page-break-after:always;

FireFox didn’t like this.  From what I found on the web the work around was to use page-break-before instead.  I searched bugzilla to try and find out more details on why this happens, the best I could find was this lengthy discussion, with instances of this problem from 2002.   So my lesson from this is to use page-break-before:always instead of after.