The Thomases are at Hen-Drefor - https://historicplacenames.rcahmw.gov.uk/placenames/recordedname/40409a2d-6197-4620-b744-5b29b90df42b
Whilst John is listed as farmer, it could have been quite a small holding and he might also have been a labourer on another farm when needs required.
The "address" Hugh Williams is at is "separate dwelling house" I'm assuming it's connected to the household listed above, which is at Pencraig. I think it suggests a small cottage or outbuilding separate to the main farmhouse, perhaps in the yard - the fact there's a collection of servants listed there would support that idea.
Thank you! Especially for the link, that's really useful!
Llansadwrn parish has the village of Llansadwrn then some smaller communities and individual named dwellings in the surrounding countryside. Ty Capel/Tyn Capel is basically Chapel House/Houses - think the building may still exist (or a successor) as a house in a row with a very similar name was advertised for rent recently. Postcode is LL59 5SR
If you go north east from Hen Drefor on the map at the link I posted above you'll find Ucheldref (see address on Hugh Williams' baptism) and "meth. chapel" ie methodist chapel, the Capel in the other address. They didn't move very far! this area matches the postcode
Perhaps, if this 1841 census return is in a similar area, maybe it is the correct one then? The ages and John's occupation threw me a little, as I said, but Grace's ages are quite off in some of the earlier censuses, so not necessarily a deal breaker, and of course, you provided a good explanation for John's occ.

Thank you, I really appreciate your help and knowledge.
