I have Cassidy family that ended up in Gateshead and Newcastle. They were from Crossmaglen, Armagh. I know of one marriage to a Garvey in the family but no McGarveys. O’Neil doesn’t ring a bell either. It may be worth looking in to.
Have you been on rootsireland.ie? It’s a pay site that has transcribed church and civil records for many counties in Ireland and I’ve made some good finds using it.
Best of luck in your search.