Hi

I looked at this when you first posted but had no answer then unfortunately.
Do you have access to Ancestry?
Someone on there has William born 1869, Mawnan and the parents of William PASCOE as;
Samuel Pascoe 1742-1792
Margaret Resuggan, no dates
It may be worth following up
There is a marriage for Samuel and Mary 15 November 1765 at Mawnan on Cornwall OPC but no baptisms to them of children

On 1841 census, William Pascoe is 70, Mary 64, Susanna 28 and there is a David 18 and Grace 1. Is this the same entry you have? So another child for them.
Christening;
David PASCOE, 12 January 1823, Mawnan, parents William and Mary.
1851 Census William has passed away and Mary aged 73 and living with son Thomas,33, wife Grace 22, daughter Ellen 9mths.There is also Cassandra Pascoe aged 11 neice to head of household, so Marys grand-daughter?All born Mawnan.
Thomas was christened 1817, its on IGI.
Trish