I'm inclined to take the "We are where we are" with this.

Its fairly clear you are going to get no joy from the vendor, so forget that for the time being.

I recently got a couple of guns from Range Right, one being a NP200. It shot like a dog and wouldn't group at all. I wont bore you with the details on what my conclusion was.

Long story short, I sent it back via my RFD. Couple of weeks later it was returned fixed. "Damaged Breech" was the culprit, which is the conclusion I came to.

If you are going to be polite and agreeable, I'm pretty sure a reputable company like Brocock will sort it for you, even if you have to stump up with the carriage.