Generally, the British and American POWs were well fed, received proper medical attention, received Red Cross food & cigarette packages monthly and played some sort of sport be it football, baseball or boxing every day. The food deprivation did not start until 1945 when Germany could not feed its own citizens, let alone the POWs.
POW camps were NOT concentration camps. Germany had enough sense to know that if they mistreated the Allied prisoners, the same mistreatment would be applied to their captured personnel. Göring went to the effort to use "his" air force (Luftwaffe) personnel to run the POW camps for captured airmen. (That is why Colonel Klink was not dressed in a traditional Wehrmacht uniform, he was in the Luftwaffe). Göring was determined to keep "those lunatics" out of the POW camps to insure proper treatment would be given to his captured airmen. Göring even had a nephew who was a B-17 pilot who flew out of England (plane name: Fearless Fosdick)
When Dr. Novak is describing the fate of his family and says "The rest is silence," he is quoting Hamlet's last words before he dies in Shakespeare's play.
When Foyle first sees Dr. Novak in his office, the music playing on the wireless is Max Bruch's setting of the Jewish prayer Kol Nidre, which is traditionally said in the synagogue on Yom Kippur, the Day of Atonement.
The record that Dr. Novak puts on just before he runs the bath is the slow movement from Chopin's second piano concerto.