Mm..
Even with this assurance, I wouldn't exactly say there are "lots" of them in the UK, as there are only four collection with them. [The aforementioned South Lakes, NCBP, and Colchester Zoo, as well as Curraghs Wildlife Park on the Isle of Man]
Though that said, London, Chessington, and Cotswolds [the latter obtained from the former] have all held the species in fairly recent times. [Up until c.2016.] Assuming Zootierliste is still accurate here, there are even more American Black Vulture in the UK, with about 12 holdings in all. [Of course the vast majority being falconries etc, the only zoo in the list is South Lakes again]. Both of the ZSL zoos, as well as Chester have also held the species fairly recently, and I also remember them being in Beale Park for some time, though I do not know when they left the collection. I would think around 2015-ish, as at that time apparently there was only one in the park.