Looking to Retire in UK or Ireland

I apologize for the long post, but I'm looking for some thoughts on retiring to either the UK or Ireland.

I am 50, American, and work in education administration. I'll be eligible to retire in 5 years and will have about 600k to buy a place and will make a fairly comfortable pension of around 5500 a month. I understand 600k isn't getting me near London, but I'm more of a small village person anyway and love Wales and the West Country. I am also interested in Ireland.

That said, I know there's no direct way to get a retirement visa for the UK. I have an odd lineage there. My grandmother was British. My father was born in the US before my grandmother and her GI husband went back to the UK and had two more kids. He lived in the UK until he was 18 and came back to the states. He does not have citizenship but is looking into it.

I've loved the UK ever since my first summers spending time with my grandmother there, and I even worked there for several summers at an American school. I have just always loved the culture, history, etc.

I guess my questions are:

* Would him getting citizenship help me get it?

* If it does, any advice on retiring there?

* And is Ireland a good option should citizenship to the UK fall through?

TIA for anything I should think about.