Hi all,
Thank you all for the help.
Margaret David was born in Margam, Glamorganshire so the marriage in 1828 in Margam could be her, but equally it could be the marriage in 1823 to John Davies in Tythegston- I'll do some more digging about her background.
I think my next mission is to figure out where Evan lived and why he wouldn't marry Margaret!
And yes, they were from what is present-day Stormydown.
Mary Lloyd eventually ended up in St Donats and married John Roberts in 1867, and they settled in Llandow.
She died in 1927, aged almost 89!
My great aunt was born in 1924 and could very vaguely remember visiting her great-grandma Mary.