I am quite convinced that the Frances Fanny Land who married Francis Wm. Deboard in Westminster in 1849 is the same Fanny living with George and Martha Palmer in Allsop Mews, Marylebone in the 1851 census. In both records her occupation is quoted as 'shoe binder'. She also appears with her father William, a shoemaker, in the 1841 census in Exeter. Her father is still in Exeter in 1851 with occupation shoemaker.
Frances Deboard is also recorded in the 1861 census living in Portsea, a very likely location for a seaman's wife.
In addition to Francis and Frances recorded as living together in Marylebone in 1871, I have found the widowed Frances in 1881 in Marykebone Lane.
I believe that Francis William died in Q1/1880 in Marylebone and Frances died in Fulham Q1/1897.

You will no doubt have noticed that Francis Wm. had an earlier marriage to Grace Elizabeth Crawford Townsend in Stepney in 1842. I think that wife Elizabeth Deboard died in June 1844 in South Hackney. If these assumptions are correct Francis William was not a bachelor at the time of his marriage to Frances Fanny in 1849.

None of these details help to establish a plausible link between Francis William Deboard and George Palmer, although logic implies that one exists.

Regards,

John