The best thing is to read memoires, there you will find plenty stories what it was like being a POW.
The stories about being POWs under the English are one of the most desperate. One of the reasons however could be that you were a POW so long, whereas being a POW of other nations, you sooner or later would have peace and prioners got free.
I was surprised - reading the very few memoires I have of soldiers - being POWs in Russia - how well they came off in the end - after surviving the first critical days. They were not burried alife in hulks but lived with a Russian community.