Nelsons in Glemsford

Richard Moss, who lives in Tyne and Wear and therefore has difficulty visiting the area for hands-on research, has approached me with this query.

My mother's maiden name is Nelson and I have, I hope, traced her family back
from (i) Greenwich, London to (ii) Glemsford, Suffolk.
However, I've now got stuck at a John Nelson (b 1797) and although I have a possible parents for him - (father William, born abt 1764 and mother Sarah Copsey born about 1767, both of
Glemsford) I'm not sure that is correct.

There I hit a brick wall.

Any help or pointers to circumnavigate that wall will be gratefully received (through me, as usual).
(There is an earlier reference to the Nelsons on this page - link via the title line, above).

SC