1911 and 1921 census records John's name as John Miller Stocks, so the M stands for Miller

1921: Born 1893, Rock Ferry

Cheshire Birth indexes for the years: 1893
STOCKS    John Miller     Tranmere    Wirral    TRA/59/69

STOCKS, JOHN  MILLER      MILLER 
GRO Reference: 1893  J Quarter in BIRKENHEAD 
Volume 08A  Page 586

Name:    John Miller Stocks
Birth Date:    14 Apr 1893
Date of Registration:    Mar 1971
Age at Death:    77
Registration district:    Birkenhead, Cheshire
Volume:    10a
Page:    64

Probate:
STOCKS John Miller of 55 Cobden Street, Tranmere, Birkenhead died 18 March 1971. Probate Liverpool 9 Aug. £785.

Norn 1895, New Ferry (on 1921 census)

Name    Margaret Corcoran
Registration Year    1895
Registration Quarter    Oct-Nov-Dec
Registration district    Wirral
Parishes for this Registration District    Wirral
Inferred County    Cheshire
Volume    8a
Page    437

Name:    Margaret Stocks
Death Age:    92
Birth Date:    30 Aug 1895
Registration Date:    Nov 1987
Registration district:    Birkenhead, Merseyside
Volume:    37
Page:    770

Norn 1920, Rock Ferry (on 1921 census)

STOCKS, GLADYS        CORCORAN 
GRO Reference: 1920  J Quarter in BIRKENHEAD 
Volume 08A  Page 1133

STOCKS, JOHN  MILLER      CORCORAN 
GRO Reference: 1923  S Quarter in BIRKENHEAD
Volume 08A  Page 877

In 2003, John M Stocks was with his wife at 132, Oriel Drive, L10 6LN, but not there in 2010