Might be of interest...
Numerous Ancient Manuscripts Confirming St. Joseph (of the Sanhedrin) Founded the British Hebrew Priesthood at Glastonbury in 36AD – St. Andrew's and St. Joseph's O.C.C.. Home of Watchman News, the Priory of Salem and TCAWW
The Culdee Church history is considered by many as simple legend. I don't consider it as all legend, and the reason mainly is because of Bible prophecy about scattered Israel, along with certain archaeological discoveries and translations of those.
To make a long story short, Bible prophecy stated how God would scatter the ten northern tribe kingdom "house of Israel", while Judah would remain in His grace in the time when northern Israel went captive by the kings of Assyria. This is written in the Book of Hosea about the ten tribes of Israel. The prophecy included the fact that the ten scattered tribes would be removed, not find their way back, and allowed to fall fully into the Baal worship they coveted while forgetting God, and He would hedge up their paths, they would forget His sabbaths and feast days, and He would lead them into the wilderness. God then called them Lo-ami, meaning 'not My people'. But then in the wilderness, He would speak softly to them, and they would no longer call Him 'Bali', but 'Ishi', and He would make a new covenant with them. And then in final the door of hope would be given them (for their final resting place with His gathering of them in final back to the promised lands).
Apostle Paul in Romans 9 quoted that final part in Hosea with God no longer calling lost Israel as Lo-ami, but instead as the living sons of God. But Paul quoted that to Roman Gentiles, when the Book of Hosea was written specifically to, and about the ten northern tribes of Israel, called after the split as the "house of Israel". In other words, Apostle Paul was speaking to Christ's Church there, making a direct connection with the scattered ten tribes of Israel and the Christian Church in Europe.
In Genesis 35:11, God promised to make of Jacbo's seed "a nation, and a company of nations". God gave Jacob the new name Israel, so that means a COMPANY of Israelite nations! This prophecy continued to Joseph's son Ephraim when Jacob transferred this blessing, saying that Ephraim's seed would become "a multitude of nations". That means a multitude of ISRAELITE nations. How's that?
Where did The Gospel of Jesus Christ take hold after Christ was rejected at Jerusalem? In the nations of Asia Minor and Europe, that's where nations began to put away their pagan idols and convert to Jesus Christ, Great Britain being the first people on a national scale to do this, after the passion of Christ (which even the old Roman Church in their councils had to admit).
Is this British-Israelism? Not really, because the "multitude of nations" prophecy does not allow one to apply this to the nation of Britain only, even though Britain with the Culdee Christian history dates back to the 1st century A.D. with Joseph of Arimathea (according to legend being a tin ore trader in travels by ship to Britain).