Hi cardiff and petercat,
Maybe the enumerator did make a mistake on the 1861 census, noting Thomas as married instead of being a widower.
As for a death of Thomas, I have this:
14/3/1872, Thomas, Evans, , 63, , , , , Upper Bridge Street
from the Trevethin Parish Record Transcripts. The 1871 census has him living in Bridge Street.
Also found on Ancestry:
Deaths registered in January, February and March 1872
Thomas Evans - 63 ? - District: Pontypool Vol: 11a Page: 113
Possibly the Thomas I'm looking at I think. Nothing else on Sarah as yet and I'll consider contacting the Pontypool Registry for a certificate as you suggest as I'd like to know.
Thanks very much for your help once again.
Cheers
Phil