Records of POW’s of various nationalities held by the French or French and their allies held by the British are held at the National Archives, Kew in document series ADM103. The records themselves aren’t searchable or viewable online.
To see the ranges available go to the National Archives catalogue page at http://www.nationalarchives.gov.uk/catalogue/default.asp?j=1http://www.nationalarchives.gov.uk/catalogue/default.asp?j=1 , then enter ADM 103 in “Go to reference” box > click “full details” tab. Scroll down and read the text especially under “content”. Then click on ADM 103/465 and click on “browse from here” tab – you can now see how the records are arranged and the piece numbers.
As you appear to be in Australia there are two options for you. Ask the NA to provide an estimate for extracting any records of his name [or close fits] or use a private researcher.
If you move up to the red menu bar and select “Research, education etc.” > paying for research you will see the NA’s charges are £1 UK per min, whereas clicking on Independent researchers will reveal a long list, many with web sites and their prices for hourly rates are half the charge, but take care about hidden extras for some.
I have no personal experience of any but you must take the trouble to check them out and the request estimates from at least 3 plus the NA, all charge extra for copies.
The NA will only look for specific records but a private researcher may follow any leads or notify you what else may be available, but the NA can send records electronically or via snail mail. In the end it will be a balance.