Agreed, but the claim of Ethiopia is not entirely based on the link to Judaism. But I would propose that we may as well leave the claim of "first" aside, it is not really the topic of this thread. Indeed, books have been written on the various claims, I don't think we are going to come to any new revelations here.
I don't think I claimed that Rome was over the British Church, all I claimed was that there was an exchange of people and ideas - and the British Church was largely in line with the rest of Christendom. I claimed that some of the early Bishops were appointed from outside the islands, but that alone does not necessarily constitute "ascendancy over" the church.
My main claim is that the Celtic Church was not completely autonomous, with a spirituality and practices that were so different than other remote or disparate Churches of the era. That is in contrast to the claim that some people make that the Celtic Church was autonomous and essentially a different branch, which really does not seem to be the case.
While the Roman church may have been more or less underground at different times, that does not mean there was no contact with the various other Christian areas, including the Britons. We know letters flowed back and forth, people traveled, ideas and discussions took place.
The fact is that the church at that time was not uniform, it took various forms and had various practices all over the places it was present. Celtic Christianity was really no different in this manner than the various observances developing at the same time in Gaul, Parthia, Ethiopia, Thrace, India, etc.