Hi
Thanks for the info on the Tithe map i.e 1839 so that ties in nicely with the 1841 census.
Richard's Will was written on 14th February 1846, just 4 days before he died on the 18th February 1846, so that means William was still at the same farm then.
1851 Census, I had the very same page (HO107) open when you sent yours so I am going with that to see how it fits.
There's a marriage between William Davies and Mary Coslet in 1842 in Llandilofawr.
Sorry but can't find him in 1861 Census.
Colin