Have you heard of 3 Bells?

[KathyM]

It is said a family member as a youngster (because he was a bad lad) was sent to "3 Bells".  I have been unable to find any reference to such a place.........(apart from modern bars).  (He was born 1911) and lived Edmonton, Barnet area.

[Neale1961]

I think it refers to old church bells.
Passing Bell: A bell rung to signal an impending death and alert the priest.
Death Knell: The bell rung to announce a death, sometimes with the number of rings indicating the deceased's gender and age.
Lych or Corpse Bell: The final bell rung as a funeral procession approached the church.

The saying may have been used as a rather over-the-top, but frightening threat (suggesting condemned to death ) to a child who had been naughty.

[Milliepede]

Yes I tend to agree.  It wasn't an actual place called that just a turn of phrase.