Thorn frames are (like most respected touring frames) manufactured in Taiwan to Thorn’s specifications, I believe, and not in house.
I know, it is quite evidently written on the frame of my Sherpa. That's why I wrote manufactured OR designed.
I think the most important thing is the design. I don't specifically care who actually does the manufacturing part, even though I wished manufacturing could be done locally, and I commend Thorn for being honest about where the manufacturing took place (unlike most other producers).
To leftpole. Maybe I misunderstood what you meant by "touring bike shop". Is Santos a touring bike shop? Koga? Tout terrain? I think there are several, particularly in Germany. Oxford Bike Works in the UK?
From my limited experience what sets Thorn apart is the philosophy of trying to educate the customer on the technical choices, within obvious constraints due to the necessity of being market competitive. They are not saints but I can see that we are talking about a small company made of people that still have knowledge of their product. Say, if I buy a Koga World Traveller I know I will get an excellent bike, but I would not know much about why it is built the way it is built, and would not be able to adapt the bicycle to my ever-changing tastes. I feel that among Thorn customers there are many people that are interesting in bicycles per se, besides their use for commuting or touring.
Maybe you can elaborate on what you meant by your original question?