I have been finding a few more records (including a branch of the Woollcott family that emigrated to Australia),
and possible fit for the death of Frederick William Cock, although it's odd that there's nothing from 1871 onwards, the location of death is a way away and the age out by a year or two:
COCK, FREDERICK WILLIAM 83 1948 M Quarter in SHEPPEY Volume 05B Page 727
No middle name there's this Frederick on the 1881 census a possibility?
Frederick Cock Age: 16 London, London, Middlesex Lodger Occupation: Shoeing Smith
RG11; Piece: 1378; Folio: 127; Page: 85
I believe this is the Frederick who died in 1948 Sheppey
1939 register Sheppey Kent
Frederick W Cock 1864
Milli E Cock there's one more person on this record
8 Jul 1893 St Mary, Stoke Newington, Hackney
Frederick William Cock age 29
father Joseah Cock married
Sophia RussBp 10 Apr 1864 St Matthias Stoke Newington Hackney
parents Josiah & EmmaHis Army records on F M P confirm above marriage and death
Service number 20167 Regiment Royal Engineers
Cock Frederick William 1864 — 1906 British Army Service Records London, Middlesex, England
children
Winifred Francis Emma 1894, Alice Sophia 1896, Francis George 1899, Albert Victor Godfrey 1902
Death certificate
15 Jan 1948 Sheppey, informant C G Cock son, 88 Alma Street Sheerness
Frederick remarried 1907
Millie Elizabeth Odell –
First wife’s children Francis George 1899 & Albert Victor 1902
Charles Gordon 1907
details can be seen on his Army Records
number 95832 Regiment Royal Engineers
Cock Frederick William 1864 — 1915 British Army Service Records Middlesex, England
It looks as if you can rule out these FWC marriages
Marriage 1887 Bath
Frederick William C(aswell) Cock father Nathaniel Caswell Cock
Ada Alberta Ashley
Banns (Bann)
Marriage Banns 22 Jul 1888 St Mary, Lambeth, Lambeth
Frederick William Cock father Frederick
Louisa Mary Brown
Marriage 1898 Paddington
Frederick William Cock age 34. M.D. his father Frederick, Physician
Frances Louisa Evans
marriage 1886 Chorlton
Frederick William Cock there's one female name missing looked at Lancashire BMD
1886 marriage Hulme, St. Michael COCK Frederick W WALKER Alice
you can view marriage cert. on family search his father William