I ended up asking and someone kindly went enquiring. She asked the churchwarden but they only keep records back to the 1950s. The oldest gravestones are from the late 1800s too.
More lateral thinking has enabled me to come one step forward and two back. I found this will. By chance, when going back over marriage records, I found one which comes with a note about Susannah's husband, John - "GROOM OF MORETON JEFFERIES".
A Prosser with a Hadland son-in-law, from what (now at least) is a tiny village. Except the names aren't matching up.
This story has more loops than a bowl of Cheerios.