The previous change I made to own_desc was not very well thought-through; it resulted in a drop-down list in which owner ids came first, and records were sorted alphabetically by those integer ids.

I've now reworked the triggers so that they produce something more useful. Script is below; I ran it in four separate operations, tested on dev and then run on live.

/* This file rebuilds the existing triggers for the own_desc field. */  
   
DELIMITER $$
   
/* First delete the existing triggers. */

DROP TRIGGER IF EXISTS `own_desc_insert`$$

DROP TRIGGER IF EXISTS `own_desc_update`$$

/* Now recreate the contents of the own_desc field. */
   
   UPDATE `owners` SET `own_desc` = CASE
      WHEN (LENGTH(`own_surname`) > 0 AND LENGTH(`own_forenames`) > 0 AND LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_surname`,_utf8', ',`own_forenames`,_utf8' : ',`own_street_num`,_utf8', ',`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_surname`) > 0 AND LENGTH(`own_forenames`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_surname`,_utf8', ',`own_forenames`,_utf8' : ',`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_surname`) > 0 AND LENGTH(`own_forenames`) > 0) THEN 
         concat(`own_surname`,_utf8', ',`own_forenames`,_utf8' : (no address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_surname`) > 0) THEN 
         concat(`own_surname`,_utf8' (no forenames or address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_institution_name`) > 0 AND LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_institution_name`,_utf8' : ',`own_street_num`,_utf8', ',`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_institution_name`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(`own_institution_name`,_utf8' : ',`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_institution_name`) > 0) THEN 
         concat(`own_institution_name`,_utf8' : (no address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(_utf8' : (no name): ',`own_street_num`,_utf8', ',`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(`own_street_num`) > 0 AND LENGTH(`own_street`) > 0) THEN 
         concat(_utf8' : (no name or street number): ',`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      ELSE 
          concat(_utf8'(no name or address)')
      END; $$

/* Now recreate the triggers. */
    
CREATE TRIGGER `own_desc_insert` BEFORE INSERT ON `owners`
  FOR EACH ROW BEGIN
	SET NEW.`own_desc` = CASE
	  WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : (no address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_surname`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8' (no forenames or address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_institution_name`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_institution_name`,_utf8' : ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0) THEN 
         concat(NEW.`own_institution_name`,_utf8' : (no address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(_utf8' : (no name): ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(_utf8' : (no name or street number): ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      ELSE 
          concat(_utf8'(no name or address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      END;
  END; $$
  

  
CREATE TRIGGER `own_desc_update` BEFORE UPDATE ON `owners`
  FOR EACH ROW BEGIN
	SET NEW.`own_desc` = CASE
	  WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_surname`) > 0 AND LENGTH(NEW.`own_forenames`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8', ',NEW.`own_forenames`,_utf8' : (no address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_surname`) > 0) THEN 
         concat(NEW.`own_surname`,_utf8' (no forenames or address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_institution_name`,_utf8' : ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(NEW.`own_institution_name`,_utf8' : ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_institution_name`) > 0) THEN 
         concat(NEW.`own_institution_name`,_utf8' : (no address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(_utf8' : (no name): ',NEW.`own_street_num`,_utf8', ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      WHEN (LENGTH(NEW.`own_street_num`) > 0 AND LENGTH(NEW.`own_street`) > 0) THEN 
         concat(_utf8' : (no name or street number): ',NEW.`own_street`,_utf8' (',NEW.`own_owner_id`,_utf8')')
      ELSE 
          concat(_utf8'(no name or address)',_utf8' (',NEW.`own_owner_id`,_utf8')')
      END;
  END; $$

DELIMITER ;