When I was young (until about 8 y/o) I lived in England and we would normally travel to Northern Ireland (where the rest of my family lives) using the ferry at Stranraer. I had some of my fondest memories on the trip there (even if it was much slower than by plane). We then moved back to Northern Ireland.

Now I'm an adult and living in England I always have gone by plane (about 3 times a year). I'm definitely going to try travelling by train+ferry now as it seems to cost about a third of what I would normally pay for a plane. Seems much less stressful too.