Is there anything else I can do to confirm the link?
There is a Katherine Sharpe is listed on the 1939 census as a widow with two children in wandsworth.
If this is indeed the right Katherine then these children would be my dads uncles.
Do you have the address for this Katherine Sharpe?
A
Katherine Sharpe living at
71 Sellincourt Road SW17 dates from 1932 up until 1965 details from
London, England, Electoral Registers, 1932-1965There are other persons with her at that address on various dates
1945 - 65 F. H Hammond
1949/50/51/52 Emma Tanner (female) &
H G Tanner1935/37 - G H T Walpole
1953-63 H G Tanner & Emma J McG Tanner living 33 Coleman Court Kimber Road London,
she died 1984 probate Emma Jane McGregor Tanner
Not sure what to make of this
Harold J Sharpe appears on his own at 71 Sellincourt Road
Harold J Sharpe Year: 1945/46 County or Borough: Wandsworth
Ward or Division/Constituency: Balham and Tooting and Central
In 1946
Katherine SHARPE and
H G TANNER (I believe this to be her brother b1902)
living at
71 Sellincourt Road SW17 and
in
1932 at that address there's an
Emmeline Jane DEAN nee SHARPE she died 1951 (possible sister of John Smith Sharpe
Emmeline married H G Dean 27 March 1910, her father Amos Sharpe occupation Brickmaker
1901 census RG13; Piece: 1299; Folio: 135; Page: 22
Head Amos Sharpe 38 wife Emma 37
Children
Amos 16, Alice 12, Alexander 10,
EMMELINE 9, Grace 8, Charles 6,
JOHN 3 Codicote Hertfordshire & Claris 1`
John has middle name SMITH on latest census
Birth certificate arrived for Maurice 
Parents John Smith Sharpe and Katherine Sarah Tanner.
I don't know if smith is a middle name or surname as they name is three separate words in a column on the certificate. I think it is a middle name.
This appears to be the birth entry of John from 1901 census parents Amos & Emma
John Smith Sharpe Jul-Aug-Sep 1897 Hitchin Volume: 3a Page: 599
Codicote is in the registration district of Hitchin