Okay RW so most of the people didn't move far but it only takes a relative few to actually transmit lore like stories. Looking at the past century alone one doesn't have to think very hard to come up with large numbers being thrown into contact with other cultures. Windrush, Prisoners of war, emigration, French gites owned by foreigners, Brits moving to Spain, European workers moving to Britain, Oriental students in our universities, seamen in foreign ports, mixed crews, Sri Lankans working in Greek hotels, foreign au-pairs. One could come up with similar lists from previous centuries.

Of course print over the last 500 years has had an enormous impact. One has only to mention the Grimms to know that. When I had a large library of folklore books a significant number of them were translations of tales from other languages and cultures.