Thank you John.
Since you brought them up I might as well deal with the Nash wills - it is a little off topic (the Woodford inscriptions) but is related to the purpose which is to identify William Hunt's wives, and there is a faint (very) clue in them.
I have the two Nash wills, plus those of Frances's father Robert Southwood 1750 and her "brother" John March 1771. Robert Southwood leaves his estate to his daughter Frances Nash wife of Matthew Nash and 500 pounds to Elizabeth Marsh wife of John Marsh, printer of Tower Hill. No wife mentioned so presumably Robert's wife (or wives) are dead. Frances Nash 1775, among an enormous number of bequests, leaves money/property to John March nephew of her late brother John March of Tower Hill and makes him executor, and to her cousin Elizabeth Rose widow and her daughter Elizabeth Crofts (the clue). John March 1771, printer of Tower Hill, leaves money to his nephew John March, brothers Richard and Thomas March, an array of nieces and nephews, and to his "good friend Matthew Nash and Frances Nash his wife" (but he does not call Frances his sister), and Mrs Elizabeth Rose. Nephew John March and Matthew Nash are the executors. Matthew Nash's will doesn't add much to the story, leaving an annuity to an Elizabeth Reading spinster and the rest to his wife Frances who is sole executor.
John March/Marsh married Elizabeth Tyees in 1743 at St Anne and St Agnes, Aldersgate where Frances Southwood and her brother Robert were born and her parents were buried. Frances's mother died in 1734, so it is quite possible her father remarried a widow March, mother of John making him Frances's step-brother.
Four tightly interconnected wills, making the marriage in 1728 between Matthew Nash and Frances Southwood almost certainly that of the will makers. This date makes them good candidates to be the brother and sister in law of William Hunt. I have been unable to find any other marriage Matthew Nash and Frances in the correct time-frame, but that could be due to missing registers or the eccentric results of the search engines of those sites that contain copies or transcripts of parish registers.
IF this is the couple in William Hunt's will, then that would seem to eliminate the possibility that Frances is William's sister, which in turn means that IF "brother and sister in law" is literally true then either Matthew or Frances are a sibling of William's second wife.
There is a potential complication from the faint clue in Frances Nash's will - her cousin Elizabeth Crofts. William Hunt's first wife Mary Cutts had an aunt who married a Crofts and produced at least two children. IF (there is lot of them!) this is not just a coincidence then it suggests William Hunt's wives may have been related in some way ("cousin" is a very elastic term).
I have not found any sisters for Frances Southwood (usual caveats apply) so Nash is the favourite to be the name of William Hunt's second wife - but it is not a strong case.