Martin, if you are unaccustomed to IOM research you won't know that illegitimate children were usually known by their father's surname, even if their parents never married.
However the IGI always enters baptisms of illegitimate children under the mother's surname even when the father's name is given and the child is entered in the parish register as [Forename] son/daur of ..... - so no surname given.
It is an extracted record (extracted from the parish register) on the IGI for AUGUSTUS FREDIC SYNNEY DIXON Christening: 02 OCT 1870 Saint Barnabas, Douglas, Isle Of Man, Father: ALFRED GEORGE DIXON, Mother: SUSAN, so the IGI transcriber thought the parents were married. So I don't know why Susan would have been known in censuses as Susan FYNNEY, as you say, presumably her maiden name.
Maude Louise Dixon's birth is on Brian Lawson's registered births index:
Maud Louise DIXON [birthdate] 21 Apr 1880, [registered] Douglas, [father] Alfred DIXON [mother] Susan KYAY ?
[Registration started officially in 1878 which is why earlier births are not usually there.]
Their other children on the IGI were:
EDITH ANNIE DIXON Christening: 12 APR 1873 Saint George, Douglas
ADOLPHUS GEORGIUS FINNEY DIXON Christening: 06 JUL 1874 Saint George, Douglas
BL's burials index has an entry for: DIXON, Augustus Joseph Fenn(cut off), 6 wks, Braddan 21 Jul 1874.
www.iomfhs.im/lawsons/LawsonBMD/burials/dz_di.html?Submit=++Diamond+-+Dixon++
You will find most burials on this website: www.iomfhs.im/research.html including extra Braddan ones at:
www.iomfhs.im/research/64-braddanburials-90735.html
I've just checked the 1881 census and Maud L. DIXON is a Boarder aged 11 months, b.Douglas with an IOM COWIN family.
Familysearch.org has:
Augustus Caesar LINNEY Head W Male 54 Leek, Stafford, England Machinist
Augustus Fredrick LINNEY Son Male 10 Doglas, Isle of Man, England Scholar
Susan JONES Visitor U Female 28 Bristol Clifton Dress Maker
Ruth HARTLEY Servt U Female 36 Dukenfield, Cheshire, England
--------------------------------------------------------------------------------
Source Information:
Dwelling Empfield House
Census Place Ludworth, Derby, England
Family History Library Film 1341828
Public Records Office Reference RG11
Piece / Folio 3461 / 103
Page Number 21
That certainly looks like your Augustus Frederick, so I see your problem. Did his father change his name, and surname to his wife's one, and moved back to England to avoid debts or somesuch? And chose his wife's surname because his son needed a surname he would recognise? (Sheer speculation.)
There was nothing saying that Susan Jones visitor was Augustus's mother.
In the 1871 census DIXON, Augustus F was a Lodger b.Isle of Man at Castletown Road Cottage, Braddan, with Thomas & Sarah RILLY (as given on Findmypast).
In the 1891 census they are in Blackpool, 260 Lythorm Rd:
Susan Fynney 38 Wid Living on her own means, b.Somerset Bath
Augustus F Fynney 20 son Articled Accountants Clerk, b.Douglas (Isle of Man)
Maude L Fynney 10 daur Scholar b. ditto
Elizabeth Dakin 27 servant b.Yorks Sheffield
She might have said she was a widow if her husband was in trouble.
That's my best guess - that he informally changed his name to his wife's surname, and the family stuck with it later.
Donna, is there a MI or other burial information for this burial?
DIXON, Augustus Joseph Fenn(cut off), 6 wks, Braddan 21 Jul 1874.
Otherwise known as ADOLPHUS GEORGIUS FINNEY DIXON (at bapt 6 JUL 1874).
Martin thinks this is another son:
DIXON, George 2 mos Braddan 8 Feb 1879
Many thanks if you would look.
Sue