The Celtic what?Wouldn't the average Briton be primarily, genetically, Celtic, however? Anglo-Saxons might have dictated the culture, but it would only overlay the Celtic genetic contribution.Kirk is definitively a Scottish word, but the surname is so common that he doesn't have to be of Scottish-descent, at least no more than 1/n-th on his father's side. I think some novels conjured for him a Native American heritage on his mother's side. McCoy again is a Scottish last name, with the same caveats. Scott, if I recall correctly, it's actually an Irish last name, identifying Scottish families living in Ireland. Grayson sounds English, but it's not the same as Celtic: the suffix -son sounds more Anglo-Saxon than Celtic, which means it is ultimately of German descent.
Look, the only thing we can reasonably talk about is culture. I think one would have a hard time proving and determining any Celtic genes and whatever the heck that meant.
And culturally speaking, the English are not Celtic. Irish, Scottish, Welsh, Cornish, they're Celtic, and some are Gaels to boot (not interchangeable, that).
Not as well as you'd maybe think or I might have hoped, alas.and the language was eventually eliminated from the Anglo kingdoms