William Beresford Wellington

Although not an ancestor, this man is the source of the surname WELLINGTON.
When he married my ancestor Esther MYERS, nee BENJAMIN, in Melbourne in 1869, his name was William Walter BERESFORD, gentleman. He said his father was Thomas James BERESFORD, gentleman, and his mother's name was Mary Ann WALDERGRAVE.
In August 1869, he sailed with his wife and her four children on Swiftsure from Melbourne to London, all listed as BERESFORD.
In the 1871 English census, he was recorded as William Beresford WELLINGTON, draper age 50 living at 44 Heygate Street, Newington, Surrey in 1871 census, born at Cheltenham in Gloucestershire. [born 1820?]. The four step-children were listed as MYERS.
In the 1881 census he was William WELLINGTON a commercial traveller aged 61, living in Camberwell, Surrey, and the step-children were also using this surname.
He died age 65 in 1884 at Edmonton in Middlesex.
It would be nice to know the origin of the Wellington surname which our family adopted.
Looking at the English census, there were five Wellingtons living in Surrey who had been born in Gloucestershire including a Mary A Wellington, tailoress, age 60, born in Cheltenham.
Living in Gloucestershire, there were very few Beresfords but a lot of Wellingtons.
Was he an illegitimate son? Perhaps he was sent to Australia on remittances and had to change his name when he returned?