Original marriage registers for Cumnor (1559-1948) are held at the Berkshire RO.
My information comes from the OFHS's publication "Oxfordshire Parish Registers & Bishop's Transcripts" by Colin Harris. I have found it invaluable with my Oxfordshire research so, yes, am giving it a quick plug!
In the book, at the end of the Cumnor section, is this comment:
See also North Hinksey, South Hinksey and Wootton regs. and Magdalen Coll., Oxford M 1728-1754
So there would seem to be the Magdalen College "connection"!
Pennie