My father-in-law, by the family name of Nicholls, comes from an old line of seafarers with relatives in the Channel Islands, Cornwall and Wales. He was explaining to me why there are so many Nicholls in Cornwall and Wales, because of the high volume of shipping between the two. Shipping metal ore was a big trade. I was curious why if all the mines were in Devon and Cornwall, and the coal was in Wales, why were all the metalworks and foundries in Wales as well, and not in Devon and Cornwall? The answer is that for (say) one ton of metal ore, you need a lot more tons of coal (even if it's the finest Welsh coal) to smelt the ore. So, it is much more pragmatic to move the ore to the fuel than the other way around.
So what? (you might say).
As someone with a Celtic ancestry, I've always been a trifle miffed with the Trad.Archaeo's (TA) toeing the party line of the Romans invading the barbarian north. But the Celts had better chariots, better technology, better science. Better lots of things. It's just the Romans had better organised military muscle, and the victors write the history. Part of the TA story repeated ad-nauseum is that fine art bronze work only came to Britain from the Mediterranean area. But why? Britain had tin, it had copper, and it had the fuel to do the refining. Any megalithic manufacturers and traders worth their salt would do the sums. Move the high-bulk raw materials the minimum necessary distance before you produce the smaller higher-value items that are worth transporting over longer distances. The Megalithic British Isles had tin in Devon and Cornwall. It also had copper in a surprising number of places. Avoca, in the Wicklow Mountains of Ireland, Llandudno, Llanymynech and Machynlleth in Wales, Alderley Edge in Cheshire, Amlwch in Anglesey, also in North Wales, Shropshire, Coniston and southwest Scotland.
Ref: http://www.copper.org/education/history ... opper.html