I don't know of any pub being actually in the village, or a previous name for the Somerset Arms, but my brother in law lives in Dingestow so I'll ask him to ask around.
One thought is that Dingestow in the census covers quite a large area, but if a death certificate says Dingestow!
What year and what name are you looking at, I can look each side ot the entry and see addresses which will give the location of the pub. On the main road each side of the Somerset arms you have farms like Upper and lower Trafaldu, Lower Tal-y-van, Red House farm, other's i can't bring to mind.