There seems to be some difference between Thule and the island supposedly inhabited by the Hyperboreans. Having said that, I'm not too sure how much credence we can place on Thule being '6 days sailing' north-west from Britain. The six days may be absolutely right but then again the term might just be a convention of the times, a convention used to express a few days sailing (if you're lucky) of less than a week (much as forty days and forty nights might mean a period of more than a month but not necessarily one of exactly forty days).

Who knows. Though less precise, ancient descriptions of places are perhaps a little more informative. When, for example, you read of, "... an inaccessible large island, vaguely located in the Outer Ocean due to the cold weather and choppy sea..." I just can't help thinking of Britain (or Ireland). It might be argued that this 'large island' is either Iceland or Greenland but did either support 'interesting' societies two and a half thousand years ago? And even if they did would they have had cultures the Greeks would have been inspired by?

The British Isles, however, had a megalithic building tradition that was already ancient by Greek standards. If I were looking for an 'inaccessible large island vaguely located in the Outer Ocean' and an island of interest, myth and mystery, I know which island I would look to :-)