I'd suggest you look up Joan D P HALL, born 1920, in the 1939 Register available on Findmypast (credits or subscription required) so as to double check the recorded birthdates for her parents and ensure that you are following the correct people.
I am suggesting you search for her as Hall rather than Oram as the latter may have been mistranscribed, and her married name will subsequently have been added to her entry.