The Reverse Lookup is designed to allow people with only a number to find out the identify of the owner of the telephone number. 192.com used to offer this service but the service has been discontinued for privacy reasons.

The assumption is that if you have a number, you can just call the number and ask them. With 192 you can do a variety of complex searches using a range of criteria such as addresses, age, etc. But, you can't reverse lookup. Yahoo has a list of sites that offer reverse lookup directory services, but all are based in the USA and not the UK