On the 1939 Register there are no relationships so you cannot assume that Edwin and Ethel were her parents.

She's on the 1921 census as Peggy Edith NORRISH-CHANIN in the Axbridge District.  It would be worth purchasing that to find out more.

I think her parents were possibly this couple.    

This looks like her birth in 1921 in Brentford but there is a death of an Edith CHANIN in the same quarter so perhaps her mother died when she was born and she was informally adopted by her Aunt Ethel, who married Edwin STONE in 1922

Let us know if you find the BROWN connection!  Good Luck

Morning Pat

Thank you for the information and i also found 2 Death records for Peggy - see below

The two death entries you've posted are identical - except for the surname so presumably both names were given when the death was registered.
When I registered my mother's death I was asked whether she was ever known by another name and she is entered twice, same surname but different first names.