It is an Excellent book and film, on a holiday in the Lakes when I was a kid after the first time I,d seen the film my Dad took me out to one of the tracks on the Cumbrian fells Franz Von Werra had navigated on one his escape attempts from Grizedale hall, he was later captured and charged in Ulverston Police station.
Another Excellent read is a book by another Luftwaffe Pilot "Ten minutes to Buffalo" by Ulrich Steinhilper see link below
Ten Minutes to Buffalo: The Story of Germanys Great Escaper: Amazon.co.uk: Ulrich Steinhilper, Peter Osborne, L.F.E. Coombs, Carol Osborne: Books