Yes, the marriage certificate seems to be my only option unless someone on this site has already researched them (there are no Smiths in our tree, most common maiden name is Elsey).
I was sent a copy of a handwritten letter sent 'To Marjorie' and signed off 'Nan & Walter' with a Yeadon address. The letter was thought to be over 20 years old and contained memories which confirm that the writer is a relative I didn't know I had.
I went to that address with no success, so consulted the Electoral Register for 1990 at the Central Library in Leeds to find their full names which lead to the wedding info via BMD.