When surveyed in 2017 will_p noted "There are two number 40s here - this one might be an annexe or perhaps actually 40A" 
https://www.openstreetmap.org/way/472428127 does NOT have its own UPRN value but does show on aerial images https://www.openstreetmap.org/way/472428095 has a UPRN 100030237539 in sequence and also 10090303586
Not sure, leaving note open