http://www.canadafreepress.com/2003/goodall060903.htm
This article mentions that six RAF pilots (including 2 Americans) flew with the Luftwaffe on the Eastern Front. They were allowed to keep their British uniforms in case of shootdown behind enemy lines. No more info.
They may have been recruited while serving as POWs.
And the discoverers of Preucil's story think that he might have had a sort of "mastermind" in the RAF - a fellow spy whose identity lies in classified files...
http://observer.guardian.co.uk/uk_ne...977780,00.html