Thank you so very much Heywood. No after speaking to her Gran, she said she wasn't sure if Phyllis was right or not. All her Gran told her was that her Grandfather was born in Ireland and that David was married to a Mabel, his siblings were a Buddy and unknown female. Other than that we know nothing. David I believe was born in India so all info I've collected re-David and Phyllis seemed to fit, marriage and probate info.
Her Gran has a lot of old photo's which she has been showing her, but haven't come across any certificates (yet). She has only just started asking her Gran about the family, so hopefully more will be revealed..
Yes, the other Cunningham family living in Westminster is wrong as they are still there in 1939 The ones in Sutton seems to be right, as this is where the family settled.
Thank you again.