"They may not have gotten as far as Britain, but one theory I’ve seen is that farmers from the Black Sea region migrated up the Danube valley after the Bosporus dam broke and flooded the region around the Sea. Same theory that others pushed east, ultimately to Tocharia. The time frame would seem to fit with this paper." I like this idea too. (Also,spreads Indo-European language) However, Oppenheimer's DNA studies (mostly) doesn't support it.