Hi Pootle, I also looked up the 1851 census for North Curry for you and discovered that there was only one John Derham and one Anne Pollard living in North Curry at that time. The two families were on the same census and living in quite close proximity to each other, co-incidentally, both sets of parent share the same christian names!!!
Here they are (fingers crossed

)
H.O. 107/1922
CENSUS No. 2
Part of the Parish of North Curry
Pages 17
Persons 154 Male 164 Female 318 Total
Enumerator John Bucknole
Page 17
76
DERHAM William 31 Farmer 6 Acres & Inn Keeper North Curry, Som.
Elizabeth 32 Wife North Curry, Som.
James 9 North Curry, Som.
Ann 8 North Curry, Som.
Harriet 6 North Curry, Som.
Mary 4 North Curry, Som.
John 3 North Curry, Som.
Sarah 1 North Curry, So
24
POLLARD WILLIAM 32 Ag. Lab. Westyeo
Elizabeth 28 North Petherton, Som.
Ann 21m North Curry, Som.
GIBBS Eliza Lodger Sister in Law 9 Lodger North Petherton, Som.