Hi Bear, if your GGrandfather fought in the first world war, you could try this link
http://www.nationalarchives.gov.uk/default.htmYou are able to look up Medal Index Cards for soldiers who fought in the 1st world war. Of course it helps if your soldier has an unusual name, and only surnames A to N are available at the moment.
Another website I have found invaluable is
http://1914-1918.org/forum/ The guys here are really knowledable, and were able to tell me my great grandfathers regiment from a photograph of him in uniform.
God luck with your search
best wishes
Di xx