Find Living Relatives

HI,I am looking for a family member called Elizabeth Ann Kelly. She may not be alive now but there will be relatives who are.
We know she was a domestic servant in Hampstead Londonin 1938,and she is not on the electoral roll then for her address which we have,so I assume she was quite young then, we know she had a close family member called Kathleen Kelly who also lived in Hampstead at that time,but we have another address for her and she was on the electoral roll so maybe an older sister,as she is on a baptism cert as godmother to a child that Elizabeth had on 2/4/1938.
Because of the accomodation that Kathleen lived in then ,we have the impression that they may have come over from Ireland around that time,as the house had a lot of people living there,including married couples. Could anyone please help,as our search has gone dry because we don't have a date of birth for either. The reason we are looking is that I am the child that Elizabeth had on 2/4/1938,I have my birth cert but still no Date of birth for my birth mother. It would seem that she kept me for a short while as the baptism cert was dated May 1938.
i am now in my 70's,and have just lost my husband, and feel time isn't on my side and have been looking for 40 yrs.
Marian