I've had an initial look for you. Firstly, they appear to be living in the village of Worle which is a small part of the Hundred of Winterstoke. This seems to be confirmed by an entry in the 1851 census where the following entry appears:-
Name Age Where born
MARSHALL John 38 Winscombe
MARSHALL Sarah 38 Worle
MARSHALL Sarah 18 Worle
MARSHALL Eliza 15 Worle
MARSHALL Joseph 12 Worle
MARSHALL George 10 Worle
MARSHALL Ellen 8 Worle
MARSHALL John 2 Worle
MARSHALL William 1 Worle
As you can see, the ages of the adults don't match up, but that's not uncommon! Apart from that, I think this refers to your family.
Sarah, Eliza, Joseph and Ellen are listed in the baptism records for St. Martin's Church, Worle.
I've tried to find records of the baptisms of either parent and their marriage, so far without success. The only Sarah I've found whose baptism is somewhere near the birth date which can be inferred from the 1841 census, 1806, is Sarah FRY baptised in Worle on 19 October 1806. There is no record of her being married in the church at Worle.
So, in general, I've not found much to help you, I'm afraid. I'll keep looking though and we can only hope that someone else has more luck than I have so far.
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