As pointed out to you in 2010 the marriage at Necton in 1832 was between a Samuel Dickason and an Ann Clark. Samuel would appear to be your Matthews brother and quite possibily Ann was a sister of Mary. The name 'Samuel' is not a mistake on the marriage record, Samuel and Ann had a son Samuel bp.9/12/1832 Necton and a son William bp.6.8/1835 Necton!
Again, as already pointed out to you, Matthew Robert was plain Matthew, wife Mary Clarke was plain Mary not Mary Ann. The 1851 census details have already been given to you and cannot locate them anywhere in 1841.
The eldest child - Hannah - was, again as already advised, bp.23/5/1836 Necton, illeg. dau. of Mary Clarke i.e. Matthew and Mary had not married then.
There are a number of online trees for this family that are somewhat up the pole to put it bluntly. Someone seems to have posted incorrect information and everyone else has just copied it. Matthew and Mary's dau. Sarah Ann for example - one tree I looked at states she was b.10/5/1843 Lambeth (which she may well have been) and bp.30/6/1844 St. George the Martyr, Southwark. I've just looked on St. George the Martyr records for 30/6/1844 and the only entry this date is a Hannah Sarah Dickeson , dau. of Henry John and Elizabeth!!!!
As to all the children you list - they didn't appear to baptise any of them in London!
The 'trees' state John was b.1839 Richmond, Victoria (when the family hadn't even left England)
Robert b. & d.1841 but no places given at all.
then comes Sarah Ann - birth regn. June qtr. 1843 Lambeth (which fits)
Mary (not Mary Ann) - reg'd Sept.1845 Marylebone
Robert - regd. Sept.1847 Marylebone
Charlotte - cannot even find a birth registration for her
As the 2 Harriet's born after 1851 do not know where they were born so can't pinpoint their birth registrations even. The last 2 would appear to have been born in Australia.
Annette