$543.00 round trip was the cheapest that I could find including all taxes, BWI to London. BWI is cheap for me to get to so I used that as a starting point. Might find lower fares if you were flexible about departures points and dates. If you could carry two or three guns over and back it would be worth the expense and trip. Best if you did it several times a year and dropped off one set of guns and returned with ones left earlier. All paper work would have to be done in advance, but that should be straight forward when you get down to it.
My problem is that I would want to stay a few days and buy more guns or worse meet others with my same double gun disease.