The excellent A Mathematician Reads the Newspaper (1995) is by John Allen Paulos and I've cited Edward MacNeil's Mathsemantics in February. Both of these books encourage you to look at numbers like those in the table above and ask do they make sense? These say that the rate of abortions is three times higher in the UK than among those giving an Irish address. I don't believe it. According to the 2001 census, there are 850,000 Irish-born people living in the UK, and there are more people on that side of the water (about 6 million) who have an Irish grand-parent (and are thus eligible to play soccer for the national team and apply for an Irish passport) than such people in the Republic. That latter number must be less than 4,588,000 because of our many wonderful-and-welcome Issei immigrants. So there can't be many young women without a friend-and-relation in the UK who will give them a bed for the night while they deal with a problem.
So, by applying common sense and internal consistency to the missing data, I reckon that the number of Irish women travelling to the UK for abortions is somewhere between twice and three times the number which is reported because it is the only number with a proper paper trail. I suppose that many (older?) members of the Catholic church would believe these missing unbaptised data have been assigned to Limbo.