Interesting article, but its what we alredy knew isn't it?
That we (the English) are a Germanic people (with a Germanic language), whilst the Cornish, Welsh and Scots (and Irish) are Celtic peoples with Gaelic languages.
I don't however think that this has much bearing these days though. Divides between the English and Scots may be cultural, or (recent) historic, but not really inherently due to ethnicity...