I doubt there is a warranty. I didn't understand why Dawes put BJ out of their misery, but they did. I would have just taken all the decals and made some Dawes that were labeled BJ. I fail to understand a lot about both of those companies. When I was a teenager, Bob Jackson was a big name in the states. I suspect a lot of people in the U.S. have fond memories of Bob Jackson. How they and Dawes got into the discount framebuiding sphere is beyond me.
I'm sure it would have helped with their hiring problems if they had been charging enough to pay people a living wage. But instead they were losing money on each frame, but making it up on volume.