There's no evidence of Celtic speaking peoples in ancient Israel, no evidence of Hebrew speaking peoples in ancient Celtic Europe, no evidence of any mass migrations from the Levant into Europe.
In fact, the whole "lost tribes of Israel" is a myth invented long after the alleged events were said to have occurred. The Assyrians never transferred entire populations; at most the elites of the various conquered peoples were transferred. The same people who were the "lost" tribes of Israel were still living in Israel when the "Jews" of Babylon "returned" from "exile" even though some of these Jews were converts and had no ancestors who lived in ancient Israel or Judah. These "returning" Jews were in fact practicing a new, "revealed" religion, heavily influenced by Persian Zoroastrianism, and they naturally pretended that the natives of Judah and Israel were "foreigners" imported by the Assyrians, because they were worshipping under the old religion of Israel and Judah, not the then newfangled monotheism of the "returning" exiles.
The "lost tribes of Israel" myth was concocted to delegitimize and to demonize the native inhabitants of Israel and Judah who had been living there since before the Kingdom of Israel existed; these peoples eventually became the Samaritans (practicing a rival form of Judaism), or they became the much reviled "peoples of the land" who were Jews but never accepted as equals by the returning Jewish "exiles". Much of the hostility between Jesus and the Pharisees can be traced back to this conflict between the Zoroastrian influenced Judaism of the Pharisees, and the older traditional beliefs of the "peoples of the land".
In fact, this use of religious myth by early Judaism (during the post-Babylonian "exile") is not unlike how the myths of Zionism are now used to delegitimize and demonize the Muslim and Christian Palestinians who have been living in Palestine/Israel for thousands of years, and whose ancestors are the very same ancient Israelites who were shunned and condemned by the "returning" Jewish "exiles" from Babylon.
Religious myths are powerful political weapons in the hands of those who are seeking entirely worldly ends.
Adding that one to my lexicon!
I just can't work up a lot of sympathy for the Palestinians these days, especially after seeing the reaction in Nablus and elsewhere to 911. It left a coldness inside.