The majority of UK residential phone numbers are now ex-directory, so most people can't be found via the Phone Book.
Similarly, the majority of people who submit their electoral registration forms now tick the box which excludes their details from the 'open' register (which is the only one which 192.com has access to). So, despite all the claims of 192.com, the majority of people can't be found through that site.
The
only complete listing of all registered voters is the 'full' electoral register. Only the police, security services and specialist agencies (such as credit reference agencies) have access to the full roll in digital format. The general public can only view the print version and only at the relevant council office. The listings are in alphabetical street order, not in name order. (So, if you only know the name, you have to go through the register street by street until you come across it).
You're usually required to make an appointment in order to view the full electoral register and you have to be supervised by a member of the council's staff when you do so, after first signing a declaration that you'll only use the information for permissible purposes. You're not allowed to make any copy of what's on the register, even in the form of handwritten notes.
(This council's website explains the position clearly:
https://www.babergh.gov.uk/elections/register-of-electors/ )