I've been looking for this couple on and off for a while, but am about to give up finding them between 1851 and 1879. But before I do, I thought I'd let rootschatters have a go.
It's just the 1861 and 1871 censuses where I can't find them (or any trace of them between 1851 and 1879).
Here's what I know:
William Graves
Born 23 Apr 1825, Newington, Surrey. Son of John & Martha Graves.
Bapt. 3 Jul 1825, Newington St Mary
Married Susanna Freeman, St Ives (Huntingdonshire) 26 Aug 1849. He was resident in St Ives, and was a waterman.
1851 census: 27 Vic Terrace, Hemingford Grey, Hunts (HO107/1749, fol. 612, p. 13). He was a bricklayer.
27 Mar 1879 he was a bricklayer
1881 census: 22 Wilmer Gardens, Shoreditch (RG11/401, fol. 90, p. 44). He was a bricklayer.
Married Hannah Brown (b. c. 1854 St Giles, Middlesex), Shoreditch St Anne 20 Nov 1881. Resident 22 Wilmer Gardens. A bricklayer.
1891 census: Shoreditch workhouse. On his own, but married not widowed (so presumably his second wife, Hannah, is still around somewhere. A retired bricklayer.
I then lose him and his 2nd wife.
Susannah Freeman
Born 22 May 1829 St Ives, Hunts. Daughter of Oliver Freeman & Anne Spencer Sisson
Bapt. 10 Jun 1829 St Ives
1841 census: Back Street, St Ives (HO107/448/11, p. 49)
2 Jan 1848 Witness in St Ives to the marriage of her sister, Elizabeth, to James Lines.
26 Aug 1849 Married William Graves, St Ives. Resident: St Ives, Occupation: Dressmaker
1851 census: 27 Vic Terrace, Hemingford Grey, Hunts (HO107/1749, fol. 612, p. 13). She was a dressmaker.
22 Mar 1879 died of bronchitis at 30 Queen St, Horselydown, Southwark, Surrey. Informant was Mary Eatton of 25 Thomas St, Horslydown.