As I have been researching the war memorials I have found the following sites useful for research.

www.ancestry.co.uk - you may need to pay to obtain some information.

Commonwealth War Graves Commission

War Grave Photographic Project

Hertfordshire Archives

Bedfordshire Archives

1914 to 1918 - This a good site to understand about the regiments.

Roll Of Honour - Rolls of Honour from around the country.
War Memorials Inventory