I believe that this land was somewhere in the Arctic Circle, possibly in northern Scandinavia. From a report by Herodotus (Melpomene, 13), we know that the kingdom of the Hyperboreans stretched so north that it reached the sea. One more element supporting this hypothesis is the labor of Hercules with the Ceryneian Hind of Artemis with the golden antlers, as he captured her in Hyperborea. It is obviously a female reindeer, as female deers are relatively small, have no horns, and cannot be paired with a chariot.
I have read of an older migration (those people reached Britain around 4.000 BC) and I know that this resulted in two kinds of people. The hunter-gatherers who were native to those parts and the farmers who had Anatolian / Eastern Mediterranean DNA. The one you mention is more recent (2.700-2.500 BC). Why do you think the ode of Pindar is related to this migration?