I ended up with:
SELECT 
	b.biblionumber, CONCAT('<a href="/cgi-bin/koha/catalogue/detail.pl?biblionumber=',b.biblionumber,'" target="_blank">',b.title,'</a>' ) AS title
FROM 
	biblio b
    LEFT JOIN (SELECT DISTINCT ExtractValue(metadata,'//datafield[@tag="773"]/subfield[@code="w"]') AS 'biblionumber' FROM biblio_metadata) AS band ON b.biblionumber=band.biblionumber
	LEFT JOIN items i ON b.biblionumber=i.biblionumber
WHERE
    i.biblionumber IS NULL
    AND band.biblionumber IS NULL