Hi Lizzieloop,
I've had a look in the St Mary/Whitchurch index but there is nothing in there unfortunately (apart from a record of Edmunds birth in 1797).
I've found an Alfred Lewis born in Cardiff in 1838 on the free ancestry.co.uk BMD search.
I'll email you the details.
Is it possible that Edmund and Elizabeth were married in Cardiff instead?
(Alfred's birth, if it's correct, is listed as Cardiff as is Edmund's death).
It might be worth contacting the Glamorgan Records Office GlamRO[at]cardiff.ac.uk (please replace [at] with @) to see if they can help.
Regards,
Bry.