OK, so in ACD canon, Doyle fucked up and accidentally changed Mrs. Hudson’s name to Mrs. Turner. In BBC Sherlock, Mrs. Turner next door is a nod to this inconsistency in the Doyle canon. Basically, in the stories, Mrs. Hudson and Mrs. Turner are the same person.
The joke is taken further on John’s blog, where Mrs. Hudson frequently comments while logged in as Mrs. Turner, and specifies that it’s Mrs. Hudson:
Essentially, in the realm of John’s blog, Mrs. Hudson and Mrs. Turner are practically the same person.
Which brings me to my point:
In ASiP, when Mrs. Hudson is talking to Sherlock and John and says, “Mrs. Turner next door’s got married ones,” what she’s actually saying is, “You two little shits gonna get married.”
You’re welcome.