I don't think Nketiah is your best example for this question tbh.
British player transfers, especially those performing well and from big clubs are very rare. You generally see an British player transfer from a big club to a lower rep club (Brewster, O'Shea, iwobi - I know he is Nigerian but he is home grown) or a young player making the move to a big club (rose, Delph, Rooney, Ramsey etc). The only big to big I can think of are like Sterling, Carrick, there's another one I forgot haha.
Furthermore British players hardly ever transfer abroad.
I would bet if Nketiah was European