If you google China Fach you find an article about a locality of Merthyr Tydfil with that name, but nothing for any other place. On the relevant census page there are 7 families (22 people) living there but no street numbers - I am wondering if it may be a large building of some sort.
I purchased the census page from FindMyPast, but when I click on the 'Next' button to see the next page I get a system error, so I can't see other entries around it. I'll try again tomorrow - thanks for your responses.
I have found out where China Fach was by looking at multiple pages of the census - it was between Neath Abbey Road and the ruins of Neath Abbey monastery. As there were no street numbers on the census pages I don't know if it was one building or a row of buildings, but on an 1876 map there does seem to be one row of buildings. Will try to find in earlier/later censuses.
Thanks for looking Dave and Emeltee