You're right, but Patrick was later than the 2nd century, so now I'm not sure where I got that information. I did just take a look at Schaff and he says Christianity did spread as early as the 2nd century to the Kelts, Gauls and some Germans but that the effects were transitory. I don't have the time to research it further right now but I'm sure I read somewhere about a very strong 2nd century Irish church, centered mostly in a monastery. Anyway, Patrick did do a great work of conversion on the Island. The Wikipedia article on him has a picture of a statue of him with that awful pope's mitre on his head.