Find Ancestors

Hello, I am hoping someone can help me, I am trying to track down my mum's side of our family tree but have hit a brick wall. My mum was born Margaret Wall in July 1929 in Marylebone, her mother gave her up to be looked after by nuns in Hackney around about 1930-31, my mum is terminally ill and i would love to be able to give her something on her family. The convent that she was taken to by her mother was called The Sacred Heart Convent, mum says this was on Hackney Road, Hackney, London but i cannot find any trace of this, she was also told after the war when she went to find her mum that she had been killed in the latter part of the war in an air raid, we also believe that my mum's mum was a nurse at the time that she gave her up, in or around Marylebone, we have looked for documentation of her mothers death but cannot find any. She believes that her mothers name was Mary Wall. Any help from anyone who has any information would be gratefully received.