BT BT Directory Enquiries
Has separate directory enquiries sections for personal phone numbers and business phone numbers.

ukphonebook.com
Directory enquiries for personal and business numbers. Users must register to use service.

NumberCheck
Users must register to use this site. Used to check single phone numbers of whole databases to ensure they are up to date for area code changes. Useful for telemarketing and other telephone based business use.

192.com
Has details of the new 118 119 service replacing 192. Use to search for people and businesses. Also find information about people on the electoral registers. Registration is required to used more advanced people search features.