This pretty much sums it up Beast. You won't have to worry about places being "bike friendly" or any such nonsense you'll be made welcome anywhere.
Given that you say above that you quite fancy coastal routes might I suggest that you sail in and out of Dublin and you could easily do most of the
Wild Atlantic Way in a week going N-S or S-N, whatever direction suits you. You could head from Dublin to Derry in an afternoon then work your way south to Cork then back to Dublin or vice versa. As I say, have a think about what it is you would really like to do and we can take it from there.
How many miles per day would you like to do? Bearing in mind of course that you won't average anywhere near the same miles per day here as you might in England. How long do you want to be out and about each day, 9am to 6pm? Once we know that kind of stuff we can get you sorted.
I will be happy to do the whole thing as a Gamin file to suit your gps if needed, once you have an idea of what you would like to do.