Shortlink output before content

I have read a number of posts on this and tweaked my code but must be missing something.

I have added a shortcode to output the standard search form on the page at http://weta.org.au/directory-search/ but it appears at the top of the page (ie is output when the function runs, not when the content is delivered)

The function in functions.php is
function search_form_shortcode( ) {
$pagesearchform = get_search_form( );
return $pagesearchform;
}

add_shortcode(‘search_form’, ‘search_form_shortcode’);

Do I need to edit the get_search_form function? or have I missed something more obvious?