I too have been searching for Sexton's in County Cork. My Sexton-1245 I can find a paper trail for, but I cannot find parental proof. My Great Grandfather had a book regarding the Sexton roots that disappeared after he passed, and I can't find anyone that will claim to have it. As I was growing up, he kept the book with high regard and it was pretty old. We were not permitted to handle it, and he did with gloves on, and when I was researching the tree in high school, we were only required names and dates. My Great Grandfather had told me that his Great Grandparents were Cornelius Sexton and Julia Donovan, and his Grandfather Jeremiah immigrated from the White Cliffs of Dover and the family had deep roots in County Cork. All I have been able to find disproves the possibility that Julia Donovan and Cornelius Sexton are Jeremiah's parents as Julia Donovan from that region was born after Jeremiah had left for the States, yet a cousin who does have my Great Grandfather's bible says that those are the names listed in it, and the bible originally was Jeremiah Jr.'s that was handed down to him when he was ordained.
I have came across a Dennis and John Sexton several times in my research from the area in the late 1700's and early 1800's, but haven't found a paper trail to connect to my line. I have also seen the surname Hayes in that era, so it may be your line I've came across.