Hello again,
Thanks for all the information you've discovered. It would seem to me that there are two possibilities that would appear most likely to be my great grandmother:
Ann DarT on the 1881 Devon Census - My mother can recall her mother Gertrude (Ann's daughter) telling her stories of when she (Gertrude) was a young girl having to curtsy whenever the horse and carriage went by as she played in the lanes. She could have been staying with her grandparents Joseph and Jane at the time in Parkham, maybe.
Annie Dark, age 28, on the 1891 Devon Census - The neighbour, Frederick Spiller, could well have been a relation of George Spiller who she married on 3rd May 1892 in North Curry, Somerset.
MMM