Have you obtained the Stanbury/Ingram marriage cert, Holborn 1840. If it is William's father with Mary Ann in '41 there's a good chance the cert. will carry father's name - it's not always guaranteed. The occupations won't match (victualler 1841: labourer 1815-1824 and I cannot read his occpn. on Mary Ann's 1826 baptism) but the address on the last 2 baptisms agree with the '41 Census.
The marriage cert for William Stanbury 1816 and Isabella Ingram is on Ancestry. Father is William Stanbury, a victualler.
Marriage cert for John Stanbury (William's younger brother) has the father as William Stanbury (deceased) victualler. Witnessed by William Stanbury, who should be my William 1816.
The occupation of victualller matches the 1841 census in Portsea for William Stanbury c1785, now a widower, living with daughter Mary, whose age matches that of the youngest daughter of William Stanbury and Ann Weable.
I don't know how William went from labourer to victualler.
On the 1841 census, William the elder says he's 50, and that matches better with the trees of the Lifton Stanburys who list them having a son called William in 1878. I'm not worried about a few years age difference on a census as I have seen so many ancestor fudge their age by up to 10 years between different censuses. The address appears to be Georges Square.
Ohh I see what you mean Baptism of Ann, daughter of William Stanbury and Ann Weable, their address was Georges Square. I can't read the occupation on Ann's baptism either, but that does confirm it's the same William being followed.