Gerard,
I am also researching the moonlighter John Twiss, and have been collecting material on the Glenlara murder and Twiss's execution for years, hoping to publish something on it. I suppose it's Pat Lynch's book you read. He's quite vague on Twiss's origins. I've come across 2 or 3 surnames for Twiss's mother. It might indeed be Chute - I haven't confirmed it yet. I haven't pursued the question of his birth in London yet, or the reasons fo the family's dramatic fall in its fortunes. As you probably know the family were C of I but might have become Catholic. Lynch probably spoke to people who knew the family when he researched it in the 1950s, but that doesn't mean his facts are all reliable. Nevertheless, several sources say he was indeed born in London.
Paul D