Ultan,
I can't remember if you covered it in your book (on loan at the moment), but there was an 'Irish-speaking only' club in Greenland Street, at the North end of Camden High Street which was said to be frequented by mainly Connemara men who had a reputation as being 'hard men'. If they heard anybody speaking 'the tongue of the oppressor' would eject the offender, often forcibly, down the steep flight of stairs.
We got this from several people, mainly musicians, who were around at the time.
Also, can't remember if you used the term 'under-the-lamp', which is still in use in my native Liverpool (or was when I worked on the docks there) for clandestine payment to avoid the tax man. It referred to the practice of subbies paying the men under a street lamp at the end of a days work.
Jim Carroll