What is the name of the directory, people not in the phone book in the uk

In the UK, the directory that includes people not listed in the traditional phone book is called the "Electoral Register." This register contains the names and addresses of those eligible to vote in elections, and it includes individuals who may not have a listed telephone number. Additionally, there is a service known as "The Telephone Preference Service" (TPS) that allows individuals to opt out of unsolicited marketing calls; however, it doesn't serve as a directory per se. If you're looking for people not commonly found in public directories, they may also be referred to as being "unlisted" or "non-published" in telephone directories.