Hi @Anonymous User
NowTV don't have every movie title and the movies that are available on their service will be there for a fixed agreed time with the movie studio.
Deadpool was on nowtv, but now has left the service (Netflix currently as Deadpool i believe).
A lot of the movie titles that leaves the nowtv service does come back sometime in the future.
Here's a link of all the movies currently available on the nowtv service when using a cinema pass.
http://www.artesea.co.uk/nowtv/movies.php