His name actually comes up as William Newson of the 197th Field Ambulance- Royal Army Medical Corps. Forces War records has several records but you have to be a member to view them. Fold 3 has his Japanese PoW index card which I have attached. Have you ordered his military records from the MoD?
https://www.gov.uk/get-copy-military-service-records

Here is a link to one of the best sites for WW2 Japanese PoW research-
http://www.mansell.com/pow-index.html

British Archives-
http://www.nationalarchives.gov.uk/help-with-your-research/r...