the church stands today, and was right on Stephen's door step - today the premises of Greggs ( Bakers) 71, Commercial St, Newport, Gwent NP20 1LR :-

St Pauls Anglican church
Commercial St
Newport, NP20
00 44 1633 266 076

http://stpauls.thelabnewport.org/about/

http://www.newport.gov.uk/_dc/index.cfm?fuseaction=thingstosee.churches&contentid=c...

St Wooloos may be the parish on your certificate

a long shot for a Ben Smith (!)
1841 Abersychan
Benjamin Smith abt 1786 Trevethan, Monmouthshire