I have had similar difficulties and been unable to find info.
I was looking for info re. (WW2) POW camps in Wales, locations and farm work locations, although I know that POWs might be moved from one camp to another (I know of an instance of someone being moved from Wales to Lincs and presumably back to Wales - though I don't know the dates or the whys and wherefores).
An uncle was a POW in Kent, again I don't know the details, only that he had a bike at a time when they were hard to come by. Such is the detail of family stories.
Have you tried local history groups in the locations where the camps were?
Again it might not yield lists of names, but the occasional 'story', probably relating more to any POWs who stayed and married locally.
And of course people with any first hand knowledge are fewer with the passage of time.
I'm not sure if I am remembering correctly, but has there been a thread about how to apply for military records for Wehrmacht soldiers which might have some info?
Though that might only help if looking for a specific person.
I'm sorry I am unable to help, but will follow this thread with interest.
Lisa