Tonight The Telegraph reports this as the official stance of the Church of England.
Comments from Dr Robert Innes, the Bishop in Europe:
There is no official definition, which reflects the fact that until fairly recently definitions of this kind were thought to be self-evident, as reflected in the marriage liturgy. The LLF project however has begun to explore the marriage complexities associated with gender identity and points to the need for additional care and thought to be given in understanding our commonalities and differences as people made in the image of God.
If anyone knows what that means...