British War Graves Commission keeps a full record of casualties for WWI along with the cemeteries they were buried in.
Of special and very personal interest you might also want to check Pierre:
(*), as I did in locating my uncle's grave in France. Pierre keeps a fantastic record along with sites and population of all cemeteries. He even went so far to send me a picture of my uncle's grave in Unicorn Cemetery.
Incidentally, no one was restricted to any particular regiment purely because of residence. My uncle, who was KIA shortly before the Armistice, belonged to the Essex Regiment, even though he was a native of Madeley, Cheshire. He had also served in a Derby regiment.
Just type in the info about your relative on the British War Graves Commision form and they will post a result immediately. You access it by typing: British War Graves Commission.
(*) Moderator Comment: e-mail removed in accordance with RootsChat policy,
to avoid spamming and other abuses.
Please use the Personal Message (PM) system for exchanging personal data.