I've never really been happy about Holmes and Watson drifting apart during Holmes' retirement either. I don't see why ACD felt he had to do that - why once Holmes had come back, Watson and Holmes couldn't have just stayed together for the rest of their lives. I mean, ACD had gone to the lengths of killing off poor, innocent, long-suffering Mrs. Watson in order for Holmes and Watson to be together. I always feel the friendship with Stackhurst indicates Holmes is missing Watson - Holmes is trying to recreate that relaxed relationship with someone else.

I must admit I don't think the housekeeper is Mrs. Hudson. I think Holmes would have given her name, and just the way he refers to her suggests to me it's a different person. There's that passage:

It was my old housekeeper who heard of it first by that strange wireless by which such people collect the news of the countryside. “Sad story this, sir, about Mr. McPherson’s dog,” said she one evening. I do not encourage such conversations...

Holmes seems to be a little snide here - using "such people" and looking down his nose at "gossip". That suggests to me that the housekeeper is of a lower social class than Mrs. Hudson. "Such people" also suggests to me that the housekeeper is local. And I think at this point Mrs. Hudson was probably travelling round the world on the proceeds of Mr. Holmes' rent anyway ^_^