Cornwall and the Highlands — Celtic territory.
One of those DNA testing ancestry websites has “Irish, Scottish, and Welsh” as a single category, but I have to think the DNA is different between Highlands and Lowlands Scotland. You could validly lump the Highlands with Ireland, but I’d think the Lowlands would be more like “English” (one of the other categories).
You may be right, and Nordic DNA in all those areas I’d bet.