He was an Anglican bishop Hope, as I am sure you know. It doesn't matter where someone was born, in Archbishop Williams's case it was South Wales, but I've not heard of a non-Anglican becoming AofC. I suppose it could happen but whatever church they belong to would have to be compatible with the CofE - and they'd have to become Anglican. I mentioned the Episcopalians but I think they are compatible with Anglicanism. I suppose you're thinking of other churches, like Methodist or CofS and I've no idea how that would work.