The BOC is supposed to be a diocese especially working with non-Egyptians, but this can only be temporary (maybe hundreds of years temporary!).
There should be one Synod in the UK, the Coptic bishops should have fixed dioceses, and the other single bishop Churches should temporarily cover the whole country as the BOC does and as they presently do. This single Synod should work hard to establish a real sense of being one Church, among both clergy and laity, so that in due course the one Synod is able to establish a multi-cultural Church in the UK with one bishop in one area, and different ethnic backgrounds represented in each congregation, with varying balances and proportions.
A single Synod would be a start. I don't know how long the rest might take.