Lost Friends Some ways to search for lost friends and relatives in UK

The Salvation Army Family Tracing Service http:///www.salvationarmy.org.uk/familytracing/

Looking for living people may have sensitive issues. People are aware of this and may not want to tell you if they know the person. Those people should contact the person and see if they want to talk to you. 

Genealogy Message Boards
Various sites have Genealogy Message Boards - with Surname boards. These are very good for finding information on your folks. BUT more to the point I have found many cousins including two first cousins (twice removed)
Hence my favourite is Genforum     http://genforum.genealogy.com/my/

But I also like the Rootsweb and Ancestry and Ancestry UK  message boards - These are the same boards but with a slightly different interface. URL http://boards.ancestry.com/mbexec/script/main/rw
These sites like you to register and this service is free. It is not part of an Ancestry chargeable subscription. (there are other places offering these kind of service but I have not used)
 I have seen people looking for current relatives

Address Lookups

Lost Friends Message Boards - many sites like this.
Entering your details is usually free - and people can contact you - if you want to contact names you see it may require a subscription usually around 5 GBP  - I am not saying you will make contact - it depends if your relative decides to access the site

This one has some useful links  http://www.lookupuk.com/
 as does this  http://www.people-search.co.uk/  the site itself will search for you but they charge.

Also do search for names at www.google.com - sometimes amazing what you find