^ God, way to make me wanna re-watch so many of HistoryTime's documentaries.
That being said I'd like to add to this bit:
for example the Ancients themselves described the export of Cornish tin as far afield as the Levant
yep. the term Britain originates from the Phoenician "baratenak" (or something like that) meaning "the land of tin" or "the tin isles". IIRC, there is archeological evidence of Phoenician traders arriving to modern-day Cornwall to buy tin and sell Mediterranean goods.
going even further back with the tin example, the main sources of tin in the Bronze Age were Britain and Afghanistan. The trade probably went through multiple intermediaries before coming to the complex core system in the Middle East and Eastern Mediterranean, but it still shows how extensive the trade networks even over 3000 years ago were.