About the tribe of Dan... I'm pretty sure that it was intermingled with the other conquered countries that were taken over by Assyria. Assyria was well-known for doing it in order to prevent rebellions. What basically happened was that the poor and uneducated people of the Northern Kingdom of Israel (Ephraim) were left in place after it was invaded. The high class population, though, including the priests and other important people, were shipped off elsewhere carefully and spread far apart so that their cultures were completely forgotten. It is doubtful that they remained long enough to reach Ireland. I don't remember anything about Israel's culture reaching others' lands as a result of the diaspora. You probably know what happened to the poor people left behind in Israel -- the Assyrians moved in some pagans and their culture and religion was corrupted. They became the despised Samaritans known in the Bible.
I don't know anything about the Hibernians, but I'm looking them up right now...
It seems they were formed in the 1500's AD as a form of protest against Protestantism. I'm not really thinking too well right now because of sleep deprivation, but I really doubt the idea of them really being descended from the Hebrew nation. According to most historians the people of Great Britain were mostly descended from the Anglo-Saxons and Vikings (not sure if they're two different groups) and Romans. Red hair comes from the Anglo-Saxon heritage, I think. People with red hair tend to be more resistant to pain, which was helpful to such war-faring tribes of people.
I'm just chock full of useless information, aren't I?

Might want to look some of that stuff up as I haven't double-checked it.