The Cotswolds, the region where this was found is west of London, in the region of Oxford University, famous for it's archeology department, and where the Ashmolean Museum is located. I think this site is on the old Roman travel route between London and what the Brits today call "The West", where so much mining activity took place during Jesus time.
Joseph of Arimethia was in the shipping business big time, hauling tin from "The West" of England to Palestine, and probably to Rome as well. As a member of the Sanhedrin, he undoubtedly had lots of business clout (and of course owned the tomb in which Jesus was buried, briefly).
Isn't this also the site of the of the tin mines of the Carthaginians (Phoenicians) of the 8th century BC? I've read that the Carthaginians ran a shipping blockade at Gilbralter to protect the source (England) of their tin.