This seems like a popular cycle route through Ireland, but I can't seem to find any info about doing an unsupported, bike-camping tour of the whole country. I drove most of it a few years ago and really wished I had done more biking/hiking/camping while there.
Isle of Arran - Arran or the Isle of Arran is the largest island in the Firth of Clyde, Scotland. With an area of 432 square kilometers it is the seventh largest Scottish island. It is in the unitary council area of North Ayrshire. In the 2011 census it had a resident population of 4,629.