The concept that you buy the gun and not the name is flawed in many ways. I can't think of any other product that follows those rules so why should guns be any different?
To the average buyer, or even the above average buyer, buying a name ensures a certain degree of quality without having to make judgments which often are done 'blind' or without adequate means.
Id the average buyer of a shotgun going to have the opportunity to spend days researching an unknown maker and make assumptions of how he came to be? Can he fully disassemble the gun to see that all parts are of the best quality? Nope.
And when he goes to sell the no-name gun he'll take a shot in the shorts just the same because the next buyer won't likely be as forgiving.
'Buy the gun not the name' is good advice for someone who 1) knows London guns very, very well and 2) wants to die owning it.