yea the best way to go is through an apprenticeship program. that sounds like a cool career. make some awesome weapons...make mine with a lazer in the future ok lol jk.
It's not surprising that all you can find is American information, I don't know how old you are but my advice would be to follow an engineering apprenticeship to start with.
I would also suggest you contact a British Gunsmith like the one under my source and ask them the same question