OK thanks. Yet another question: the code from qa-page-tag.php only returns one page's worth of tags by default:
list($questions, $qcount)=qa_db_select_with_pending(
qa_db_tag_recent_qs_selectspec(null, $oldtag, 0),
qa_db_tag_count_qs_selectspec($oldtag)
);
I used "1000" as the $count parameter - i.e. (null, $oldtag, 0, false 1000) - as an interim hack but is there a way to actually get all the posts with a particular tag?