I would disagree with the statement that English Goalkeepers were the best of their era. Except the incomparable Gordon Banks who was as safe as the "Banks of England" no other english keeper can stake that claim. Banks was acknowledged as the best keeper of his era by none other than PELE.
Both Shilton and Seaman were fallible on the crosses. In fact during Peter shilton's time there were much better goalkeepers fm other countries like toni schumacher of west germany, joel bats of france, rinat dasayev of USSR, pfaff of belgium and pumpido of argentina.