How do I find out where my Grandfather was kept as a POW. He was in the East Surrey Regiment but that is all I know.

Your better off with the following website and the forum attached to it has all the experts you could wish for to help and answer questions.

http://www.1914-1918.net/index.htm

Thanks for that, its almost impossible to find out about pows, as most of the records were destroyed during WW2.