According to the "Life of George Chaffey", Frances Elswood, or Frances Allen Elswood as you call her, was supposedly the daughter of a clergyman, the Reverend Mr Elswood, by his wife Frances Allen, great-niece of Dr John Allen, sometime Master of Dulwich College, near London. This is a little curious as the Chaffey family (at least this line) was one well settled into 'old dissent', i.e. Presbyterianism or Congregationalism. There is, by the bye, a gentry line at Stoke-sub-Hamdon which must be related and which had always conformed to the Established Church. Of course, for Frances Elswood's father to have been a clergyman, he need not have been an Anglican parson, though one might have expected Chaffey's biographer in the 1930s to have called his forebear a 'dissenting' or, at least, a
'nonconformist' clergyman were he one. Then there is the small matter of the Reverend Dr John Allen's definitely being an Anglican. His niece (or great-niece depending on how one interprets the passage) would not be expected to have married a dissenter. It seems far more likely that Frances Allen married a C. of E. cleric, and that it was not until her daughter was wed that anyone married a nonconformist, in this case the nonconforming layman, Benjamin Chaffey, woollen draper, of Stoke-sub-Hamdon,rather than she herself, Frances Allen that is, marrying a dissenting minister. Any marriages to clergy or layman, Anglican or members of most of the "independents" must, at any rate, have been married according to the rites of the State Church, as was required by law at the time for everyone save Jews, Quakers and Roman Catholics. There is hardly any question that the father of Frances Elswood did not belong to any of these latter bodies. Comment would certainly not have failed to be made if he were such, and a clergyman (though the Quakers have no clergy while Rome's don't marry after surpassing the diaconate to the priesthood, and it scarcely seems likely that it was to a Rabbi Elswood that Frances Allen married given the strict rules against intermarriage with non-Jews then prevalent in Judaism, and the disqualification as to Jewish status for any children born of a union between a Jew and a non-Jewess even in the present age, and the even greater unlikelihood that Frances Allen was a convert to the Hebrew faith.)
Turning then to likelier lines of enquiry, I have found a possible candidate for Frances Elswood's clerical father in the person of one Clement or Clemens Elswood, who was sometime rector of Ibberton, Dorset. According to his biography, below, he unfortunately appears, at least at first glance, to be a generation too old, minimum, to have sired Frances. He lived 1707-1775 and was the son of Richard Elswood, of Wayford, Somerset. See the "Alumni Cantabrigieses" (Cambridge University Alumni Registers by Venn) entry, viz.:
Elswood, Clemens, M.A. from KING'S, 1751. s. of Richard, of Wayford, Somerset. Matric. from Wadham College, Oxford, Dec. 17, 1726, age 19; B.A. (Oxford) 1730. Ord. deacon (Bath and Wells) Sept. 20, 1730; priest, Sept. 24, 1732. R. of Ibberton, Dorset, 1752-75. Chaplain to the Earl of Berkeley. R. of Corton Dinham, Somerset, 1755. Died Nov. 9, 1775. M.I. at Ibberton. (Al. Oxon.; Hutchins, IV. 361.)
See a fine old Church of England pluralist in the best Trollopian tradition!
I don't have Foster's "Alumni Oxonienses" on hand at the moment, so I cannot check the Reverend Clemens Elswood's Oxford record or whether he had sons who went there (who could have been father to Frances Elswood wife of Benjamin Chaffey). Of course, in a pinch, she could have been his daughter born either before his death in 1775 or even posthumously. That would, of course, make her older than her husband, Benjamin Chaffey, by a number of years, but this has been known to occur. The reverend gentleman could have begotten a daughter in old age by a younger wife. Perhaps the biographer of George Chaffey did not know this or passed over the detail with greater delicacy than I.
It would be useful to check the parish registers of St Eustace's Church of England parish church, Ibberton, Dorset, to see what trace there may be of the Reverend Clemens/Clement Elswood's family there. Similarly, Wayford and Corton Dinham need surveying. One imagines that there should be some information on him and any family he had there, especially given the lengthiness of his incumbency: that is, of course, if he were married.
I hope that these remarks/ruminations are of interest.
Vancouver, British Columbia