Can you confirm that this entry in the 1939 Register is of the family you are seeking:

Benjamin S Stevens
Gender: Male
Marital status: Married
Birth Date: 30 Jul 1907
Residence Year: 1939
Address: 16 St Olave's Walk
Residence Place: Mitcham, Surrey, England
Occupation: Clerical-Insurance
Schedule Number: 134
Sub Schedule Number: 1
Enumeration District: CNAE
Registration district: 31-1
Inferred Spouse: Olive M M Stevens
Inferred Children: Stanley T Stevens
Maureen Olive Stevens
Patricia M M Stevens
Household Members:
Name
Stanley T Stevens
Hilary T Enoch
Benjamin S Stevens
Olive M M Stevens
Maureen Olive Stevens
Patricia M M Stevens
This record is officially closed.

The date of birth quoted in the Baptism Register is match:
Name: Benjamin Stanley Stevens
Baptism Age: 0
Record Type: Baptism
Birth Date: 30 Jul 1907
Baptism Date: 9 Oct 1907
Baptism Place: St Bartholomew, Dalston, Hackney, England
Father: William Robert Stevens
Mother: Harriet Stevens

and is this Benjamin's marriage:
Marriages Sep 1932
Stevens Stanley B White Wandsworth 1d 1444
White Olive M M Stevens Wandsworth 1d 1444

If so this would suggest he stayed in London possibly with family?

Mike