Buster 11:
You need to start in The National Archives (used to be the Public Records Office) at Kew. Some of their records can now be downloaded so you might not even have to go there. I last used the service a couple of years ago when I was researching the demise of my grandfather at the Battle of Aubers Ridge in 1915. I was able to download all of the relevant War Diaries at a cost of something like £3.10 per download.
So, to get you started you need to go to:
[url]www.nationalarchives.gov.uk/
Select the National Archives 'Discovery' option.
To get you moving in the right direction, type WO 344 into the search bar.
That should take you to the section which holds the General Questionnaires For British/American Ex-Prisoners of War.
You might find some further information in the WO 208 section.
Secret Statements etc can be found in AIR40/1533
Commendations in AIR40/1491
Special Notations in Personal Records in AIR40/268
Happy Hunting.