Thanks, guys - great stuff. In a way, the responses reminds me even more of "1066 and all that", specifically that book's subtitle "the decline and fall of practically everybody".

I guess we know quite a lot about changes in terms of politics, language and culture. What is intriguing at a human level are the physical population movements and shifts - e.g. the what happened to the Britons when the Anglo-Saxons moved in etc? The kind of DNA evidence Kraxis mentioned about the Scythian/Mongol is fascinating.