Tracing War Graves
If you are trying to trace someone missing in action, the first place I started was the Reference Library (ask at your local library where the nearest one is). Here you will find reference books to every military personnel that was killed or missing, in both world wars.
You need the name, approximate date and location of the last know place they went missing. There are a lot of books (and I mean a lot, so expect to spend a great deal of time) covering different areas. It's just a matter of looking through the alphabetically listed books until you find the correct person (name, number, regiment, date of birth, age and parent's names with their last known addresses) are all documented. Librarians can be very helpful if you ask.
If you manage to find the correct name and anything is known about that person, it will be listed. Every burial is catalogued with the Cemetery (the exact burial plot, and instructions how to get there). There are also a couple of paragraphs about the area, battles, troop movements etc.
Update: You can now do a search online at www.cwgc.org (Commonwealth War Graves Commission) and get the same details as above.
Every serving military personnel were awarded medals, and you may still be able to get unclaimed medals if you are a close relative. The new address to write to is:-
M.O.D. Medal Office
You will need the written consent of the next of kin to receive the medals, and proof of your relation to the person. They may also ask for the death certificate, which you can obtain from your registry office or Somerset House.