On page eleven of the copy of the book I have, Scout is discussing the story of Boo Radley and the reasons why their house was shuttered all the time and no one knew what went on in there. But part of the discussion involves the fact that Boo Radley, as a youth, had hooked up with the Cunninghams and was drinking and carrying on. In the narration she says that the Cunninghams were an "enormous and confusing tribe domiciled in the northern part of [Maycomb] County."
It is not entirely clear where Old Sarum is in relation to town, other than being to the north, but it is not far since the Cunninghams walk everywhere, including to school.
Miss Stephanie's house is in the Finch's neighborhood and on their street. On page eleven it says that she was "the neighborhood scold" or gossip when Scout continues to tell the story of Boo Radley.