The United Kingdom consists of England, Scotland, Wales and Northern Ireland. You can easily locate someone in the United Kingdom by using their last name and the city in which they live. BT, the largest telephone company in the U.K., provides a complimentary service online that helps you look up someone's address in that part of the world.

Open the Internet browser on your computer, and visit the BT residential number search page listed in the Resources section.

Enter the last name of the person you are trying to find in the U.K. Enter the city or area of the U.K. in which they live, and click "Search".

Scroll through the search results to find the person for whom you are looking. The address is listed under the person's name and telephone number.