I think the best, well the first thing for you to do is, tomorrow, when the church records go online ~
You need to go to St. Audeon's records and trawl through them until you find John & Mary's marriage ~ you have the date so that's a great start.
See is there anything else to be gotten from the actual register.
Sometimes extra info is on the church register that isn't on the civil cert.
Best Of Luck !
Tara