HG, glad that I might have been of some help.
The sources I have found say that he was a PoW, and since one of them is Christopher Shores, I have a very high degree of confidence that this will be correct. To be absolutely certain, though, some digging about in the PRO (sorry, National Archives) would be necessary.
That said, I should've thought that a record of where he was held captive could very well be with his personal records (I have heard, third or fourth hand of one case where it wasn't). If this is our chap, I believe that there is a 69 Squadron association, and if it is still active, it may be possible to find out what happened to F/O Booth via that route.