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
He died at the age of 77 on March 10th, 1971 in Birkenhead.3
Death Notes
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.
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
She died at the age of 92 on November 24th, 1987 in Birkenhead.3
Death Notes
Name: Margaret Stocks Death Age: 92 Birth Date: 30 Aug 1895 Registration Date: Nov 1987 Registration district: Birkenhead, Merseyside Volume: 37 Page: 770