I've finally got back to the records office! I found a burial for Richard Llewhellin, aged 31, on the 25/07/1825, in the Talbenny Parish Register. Also found a baptism for Martha Russan, 26/05/1793, the daughter of Peter and Elizabeth Russan, in the Talbenny Baptism Register. There was a Richard Llewhellin, married to Ann, in Walton West, but obviously not my ancestor. Richards death in 1825, makes the marriage of Martha Llewhellin in St Ishmaels look even more interesting. On my next visit I will take a look at that, and the other Llewhellins you found in Talbenny.