This is an interesting thread to me. I don't know much about the English gunmaking biz other than what I've read here and there. But I've spent all of my working life in and around the manufacturing biz, mostly aerospace, but some commercial mfg as well. That's why this thread captures my attention.
I did buy the H&H video. It touched on bits of the manufacturing here and there that the video producers thought would be of interest and it contained little detail and no surprises to me.
The points brought up about maintaining brand/nationalistic integrity and the point about ethnic predjudice all ring true to me. Our predjudices (forward projection of our past experiences) are what we base most of our daily decisions on, including purchases. The older we get, the more past experiences we have and the more 'predjudices' we have...right or wrong.
Outsourcing at any level, has pitfalls and advantages. The old aircraft makers in the golden age of aviation realized the pitfalls could limit their progress, affect their reputation, or bring their production to a standstill and sought to control those things by making as much in-house as possible. I see a parallel of that concern by some of the big name London gunmakers as well.
A great example of all the benefits and pitfalls of outsourcing by a highly held brand is the Boeing 787 project. It has had delays due to outsourcing and will also reap many benefits from it in the long haul.