Ah, let us return to the ?original? British traditions of the Celts! This is an attractive and romantic idea and there have been various attempts to demonstrate what those ?original? traditions were.....all singularly unsuccessful.
There obviously was a pre-Roman Christian tradition in the British Isles. The problem is that there is very little evidence as to what how it manifested, let alone sufficient evidence to allow it to be reconstructed.
At an international conference on Early Christian Spirituality some years ago I gave a paper on this question (with Rowan Williams in the audience, which gave me some sense of nervousness!), and concluded that while it may be possible to ?reinvent? or ?recreate? British Celtic Christianity, it was not possible to ?resurrect? it simply because of lack of original material, even regarding liturgy. Contemporary attempts to do so (like the so-called Celtic Orthodox Church) are modern fabrications based on little original material and much modern imagination.
In a real sense, the comment that the earliest British Christianity that could really be ?revived? would be that of Rome is correct. It is, more or less, possible to revive the ancient British Roman tradition, certainly in terms of liturgy. This has been, to some extent, what some of the Orthodox Western Rites have attempted to do, using the earlier Roman Rite (and what they call the Liturgy of St Gregory).
So, John, your friends comment was probably correct. Using old Roman liturgical forms and, for example, vestments, would follow a more authentic and ancient British tradition than using an Orthodox liturgy (which, however ancient in itself, is very modern in terms of British) and Coptic vestments which first appeared in Britain probably in the latter half of the 20th century.
I agree that an attempt to explain, if perhaps not to define, what we mean by British Orthodoxy is important. Why, for example, are we not English-speaking Russian Orthodox? Or members of either the ROCOR or Antiochian Western Rites?