Treatment of Allied POWs (at least those from the West) in German POW camps was largely professional.
Here's the text of an excerpt (7:10-7:28) from the above interview with Walter Morison, a British former POW held at Sagan and then Colditz.
Well, you see, if you were a British officer, or, come to that, an American officer, the treatment which you received (from, in our case, primarily the Luftwaffe), was so correct and indeed friendly, really, that you didn't expect anything unpleasant.
The watercolor on the left was painted by British POW Major W. F. Anderson in 1941-1942. The photo on the right shows a similar view from 1995, after the castle had been restored closer to how it looked during medieval times. The accompanying text describes how music was used as a signal during an escape.
The site features a small art exhibition and other information, often in English and German.
Mario Bosch has a great photo gallery, though his image of the castle as it was during the war (and several decades after) is on a different page.
The prisoners of Colditz are high-spirited and eager to needle the Germans. The escape officer of the British contingent, Patrick Reid (Mills), assists in the escape of other prisoners and finally carries out his own escape. The culmination of his escape, his successful crossing into Switzerland, is not depicted in the film.
Amazon.com lists a Region 2 DVD of the film (which may not work in North America).
Almost all of the events depicted in the series, except for dramatic points like the Kommandant's son and Colonel Preston's wife and mother, have a basis in truth. Most of the characters are loosely based on one or several actual persons. The most obvious are Pat Grant (Patrick Reid) and Hauptmann Ulmann (Reinhold Eggers).
Here's an interesting bit of history that shows how cultural differences can affect how a good deed is perceived:
The introduction of corn and corn flour beginning in June into the German diet was taken by many Germans as a form of reprisal, since until then corn had been considered in Germany only suitable as feed for chickens.
(I heard this story in the past, perhaps from my Uncle.)
Life was not easy after returning to Germany. Here are two letters from former POWs at Camp Aliceville in Alabama.
June 8, 1947
I often think on the days I spent in Alabama as a prisoner of war. In this time I never was hungry. But today in Germany I am always hungry. There is very little bread, we have no potatoes, no flour and no sugar. We have also very little fat and dripping. There are days, my mother does not know what to cook for the family. But we hope it will be better in autumn, when the harvest is brought in. But I think till this time, there will be very bitter days. When I am hungry, I often wish to be a prisoner in the U.S.A. That’s very sad. That’s the same with the clothes. When [I became] a soldier I was a young man and no[w] all my clothes are to[o] small. I am very glad that there is now summer. But what will happen in winter?
Tubingen am Neckar
September 15, 1947
For a long time I was PW in the camp [at Aliceville]. Often I have gone through your town. I am sorry that I was not able to speak often with the American people, but I can say, that I have been treated there very well. Now I am discharged. When I came to Germany, [I discovered] that I have lost all and often I must think of the good li[f]e, we have had in your country. Although I was a PW at that time, I have not to take care for [clothing] and food. Both are very scanty here.
A story worth sharing, from American POW Robert M. Fecht:
As you know, or have heard, the Nazi’s had no love for the Catholics. Our Commandant, who must have been indoctrinated by Hitler himself, had a very special dislike for them.
One Sunday, when the Commandant was supposed to have been gone, one of the guards, whose name was Herr Engle, called me into his room. Upon entering, I noticed a woman sitting at a small table. She smiled as the guard shut the door, motioning me to be quiet and, at the same time, she handed me a small sugar bowl full of strawberry sauce. Thinking the world had come to an end, I hurriedly ate them. I don’t think anything tasted as good to me as they did right then.
Then, to my astonishment, she pulled out a rosary and pointed to herself and the guard and said, "Catholic." I looked at the guard and he nodded and was all smiles. Just then, the door opened and there stood the Commandant.
Allied aircrew shot down during World War II were incarcerated after interrogation in Air Force Prisoner of War camps run by the Luftwaffe, called Stalag Luft, short for Stammlager Luft or Permanent Camps for Airmen. Stalag Luft III was situated in Sagan, 100 miles south-east of Berlin, now called Zagan, in Upper Silesia, Poland.
It must be made clear that the German Luftwaffe, who were responsible for Air Force prisoners of war, maintained a degree of professional respect for fellow flyers, and the general attitude of the camp security officers and guards should not be confused with the SS or Gestapo. The Luftwaffe treated the PoWs well, despite an erratic and inconsistent supply of food.
the Luftwaffe was (the least Nazified of the three German forces)
I haven't read much about the other Stalag Luft camps, but this note is interesting:
Compared to other prisoner of war camps throughout the Axis world, it was a model of civilized internment.