An interesting article from BBC focusing on migration from Europe to Briton and the replacing of the Neolithic inhabitants that built Stonehenge.
As one professor states in the article, "Up until then, the people of Britain had cut themselves off from the continent - 'Neolithic Brexit'. This is the moment when Britain re-joins the continent after 1,000 years of isolation - most of the rest of Europe was well out of the Stone Age by this point."