Excellent post Don.
I would only quible on two points.

1 "British troops became involved in the latest troubles was not by invasion, but at the insistence of the predominantly protestant loyalist majority"

I would have said that they came to protect the Catholic people from that majority protestant population, especially from the B Specials.
The reason that they had to stay after that was sorted out, was to counter the insurgency of the PIRA.

2"I really don't think, if the majority want a United Ireland, Westminster will be too upset."

I think that Westminster, and the whole country, will be overcome with glee!