There is a website called Passive House Database. I'm not sure if this is official data or not, or if all the passive houses are on the site, but if you do a search for certified passive houses in the UK, it shows 144 buildings. The list can be viewed here: https://passivehouse-database.org/index.php?lang=en#s_deaf31d37d62a701b96c42a0e8563cdd
There is also a map of the passive houses around the UK here. I don't know whether it's up to date or not though.