« Reply #1 on: Monday 18 September 06 22:33 BST (UK) »
How old are they? If the marriage was before 1837 it would have been the established church and therefore St Mary's as it looks like it's the only church that's old enough. St Mary's has deposited records and they are available from Glamorgan Family History Soc and Glamorgan Record Office. If you have a look at the Genuki page for Margam parish, it lists the various churches and there's a link to the chapels.
Cornwall: Allen, Bevan, Bosisto, Carnpezzack, Donithorn, Huddy, James, Retallack, Russell, Vincent, Yeoman
Cards: Thomas (Llanbadarn Fawr)
Glam: Bowler, Cram, Galloway, James, Thomas, Watkins
Lincs: Coupland, Cram
Mon: Cram, Gwyn, John, Philpot, Smart, Watkins
Pembs: Edwards (St. Dogmael's)
Yorks: Airey, Bowler, Elliott, Hare, Hewitt, Kellett, Kemp, Stephenson, Tebb