Here's some further information relating to the family of Frances Bennett which I hope will allow me to identify her father [or at least narrow down the search]
Her son Thomas Hamilton Durnford died in Bristol in 1822 and left a will written in 1791 in which he described himself as "Thomas Hamilton Durnford of the City of Bristol, Grocer (late of Shaftesbury)"
In this he mentions several key people, the first of these is his mother who he describes as "my mother Frances the wife of James Thomas"
He also mentions his elder sister Frances describing her as "my sister Frances Ryall (the wife of the Rev. Narcissus Ryall, Clerk)"
This Frances was Frances Durnford who married my ancestor Narcissus Ryall of East Lydford.
Now the interesting thing is that he [Thomas Hamilton Durnford] names James Thomas of Shaftesbury and Walter Whitaker [of the same place] as the 'executors and administrators' of his will. However at the end of the will amongst the probate details is a note which upon reading it seems to indicate that Walter Whitaker died in the lifetime of Thomas Hamilton Durnford and that James Thomas 'renounced the probate' [did he refuse to do it?]. At the end there is the following statement:
"Walter Whitaker died without having taken upon him the Probate & Execution thereof Francis Thomas (wife of James Thomas) deceased whilst living the mother of the Universal Legatee for life named in the said Will died in the lifetime of the said Testator"
Given that a few lines earlier Thomas Hamilton Durnford's sister Frances Ryall is described as the 'Universal Legatee' we can establish that 'Frances James' was her mother [i.e Frances Bennett who married Samuel Durnford and then James Thomas]. Also given that she is apparently alive in 1791 when the will was written, but died in the lifetime of Tomas Hamilton Durnford we are apparently looking for her death between 1791 and 1822. At the moment I have found one possible death in 1800 but I have to double check that. Also James Thomas himself may have died in 1786 as there is a burial for a James Thomas in Shaftesbury in that year.
At the moment it looks like Frances Bennett might have been the daughter of William Bennett or his brother Rev. Benjamin Bennett. However given that Benjamin was a member of the clergy I doubt that he had children. The other possibility is that Frances was the daughter of William and Benjamin's other brother John Bennett.
I'll need to investigate a few more wills but will update this asap. In the meantime any ideas or suggestions would be welcomed.
Matt