Celtic is more of a cultural than ethnic group,the Irish,Scottish and Welsh have had more admixture from invaders and settlers than the English.
If we look at Roman accounts of northern Europe they were reported to be tall with blonde or sometimes red hair and blue eyed.
Me and the Mrs done one of the tests,mine was about about 50% English 25% Scandinavian and the rest Italian,French and German and 1.2% Algerian
hers was English,Scandinavian and Spanish in near equal parts,no mud blood present.
i'm not sure how much I trust it though,my ancestors conquered the world,they may well ha