The boarding house is in Mill Pond Bank.
Pip decides to hide Magwitch under the name of Provis. He chooses Herbert’s fiancée Clara’s boarding house, because it is out of the way, near the water, and has no association with him.
It was called Mill Pond Bank, Chinks's Basin; and I had no other guide to Chinks's Basin than the Old Green Copper Rope-Walk. (ch 46, p. 253)
Clara lives with her father, who called her back from school when his health turned. It is Mrs. Whimple’s house, and she provides loving support to Clara. Provis’s room has an east-facing window and can see Pip pass by to signal him. Pip and Herbert assume that no one will find him there, and that Pip can visit him if he’s careful.