The Oct. 8 entry in this diary also has some fine info on Gradel's crash:
http://412th.org/archives/Van%20Kirk%27s%20Diary.htm
There's talk here of a Frenchman. Either the P-47 came down just across the border in France indeed, or Gradel assumed he was in France when having met a French-speaking Belgian. French is the language of southern Belgium after all...
Regards, Leendert