Interestingly, I just attended my first Episcopalian wedding several
weeks ago. I hadn't given much thought to the consistency provided by
the Deacon, etc., but in searching around, I found that, as you
suggest, there is a standard text for the ceremony.
WeddingDetails.com lists ceremony details and the text in full for an
Episcopalian marriage ceremony:
The page at that link is strangely headed as "Protestant Wedding
Traditions" but the entire content of the page is devoted specifically
to the Episcopalian ceremony.
The text is quite long and is available in full at that URL. I've
reprinted the first paragraph here:
We have come together in the presence of God to witness and bless
the joining together of this man and this woman in Holy Matrimony. The
bond and covenant of marriage was established by God in creation, and
our Lord Jesus Christ adorned this manner of life by his presence and
first miracle at a wedding in Cana of Galilee. It signifies to us the
mystery of the union between Christ and his Church, and Holy Scripture
commends it to be honored among all people."
It continues into the marriage vows with the Episcopalian "I will"s
(which several weeks ago struck me as different in comparison to the
more commonly-known "I do"s.
Please let me know if you have any further questions.