A word for my readers on the left wing of the Reformation, which is by no means exhaustive and subject to amendment and correction, particularly by my Independent Catholic readers.
The British Orthodox Church is a small Oriental jurisdiction; that is, they recognize the authority of the first three ecumenical councils but not the later four widely accepted in Eastern Orthodoxy and in the Western Church. (While almost all Unitarian Universalists renounce the creeds of those early councils, our ideas of ministerial jurisdiction and collegiality echo back and perhaps depend on the rules they established.)
The "heartland" of the Oriental churches is from Egypt and the Horn of Africa through the Middle East to India. The great antiquity and mystery (to the West) of these churches have long made them a subject of study and exoticism. They also make a lively challenge to post-Puritanism as an authentically primal form of Christianity. Little wonder one finds the occasional weary Unitarian looking East when the first Oriental missions reached the West more than a century ago. (And as an inspiration to Unitarian liturgists like Frederic Henry Hedge, who used the Alexandrine Liturgy of St. James as the core of his communion rite; this is how I came to study this.)
Like today's "commercial" yogis, missionaries for this ancient wisdom often had their own ideas about its application. Many were far from theologically orthodox. There was little structure or oversight, and the nineteenth century distance from the United States or England to Syria or Malabar was very far indeed. Let it be understood that churches like these could be, charitably put, quite eccentric.
Which is what makes the British Orthodox Church something of a success story. It put away some of its particular ways -- how much of a change this is I cannot say -- and has been habilitated into the Coptic mainline. So in Britain today there are sibling churches of Egyptians, Ethiopians, Eritreans and native Britons. (To simplify the ethnic situation there.) So the British church worships in English, has a British outlook and ethos and has a great company of saints native to the British Isles in its calendar.
It's small, and has a mission to welcome new believers. So let's next consider the mechanics of their fellowship.