$sql = "INSERT INTO " .  $wpdb->prefix  . CFTP_MAL_HOUSE_MAST_TABLE_NAME . "
            SELECT h.UPRN,
                   m.Site_Id,
            --     m.Xcoord, m.Ycoord,
            --     h.Xcoord, h.Ycoord,
            --     h.Xcoord - m.Xcoord AS Xdelta,
            --     h.Ycoord - m.Ycoord AS Ydelta,
            --     (h.Xcoord - m.Xcoord) * (h.Xcoord - m.Xcoord) AS XdeltaSquared,
            --     (h.Ycoord - m.Ycoord) * (h.Ycoord - m.Ycoord) AS YdeltaSquared,
                   SQRT( (h.Xcoord - m.Xcoord) * (h.Xcoord - m.Xcoord) + (h.Ycoord - m.Ycoord) * (h.Ycoord - m.Ycoord) ) / 1000 AS Distance
            FROM " .  $wpdb->prefix  . CFTP_MAL_HOUSEHOLD_TABLE_NAME . " AS h, ".
          $wpdb->prefix  . CFTP_MAL_MAST_TABLE_NAME . " AS m " . NL ;
        if ( 'house' == $house_or_mast )
            $sql .= "WHERE h.UPRN = %s" . NL;
        else if ( 'mast' == $house_or_mast )
            $sql .= "WHERE m.Site_Id = %s" . NL;
        $sql .= " AND SQRT( (h.Xcoord - m.Xcoord) * (h.Xcoord - m.Xcoord) + (h.Ycoord - m.Ycoord) * (h.Ycoord - m.Ycoord) ) < 1000";
        $sql .= " ON DUPLICATE KEY UPDATE Site_ID = m.Site_Id ";