If they were taken during WW2, the copyright period then was 50 years, not 70, so they would be out of copyright around 1995, one would think.
In any case, copyright on photos didn't usually exist until the 1960s, so this may just be a case of 'rubber stamping' everything, at the time.
Don't you have a Copyright Council (or equivalent) in UK that you could ask?
Dawn M