Hi Michelle
With respect to your question
"How careful or stringent were the Welsh census in requiring that ages and
birthplaces be correct?" The quick answer is not very.
We have some that have aged from 5 to 15 years between census years and some have even
gotten younger. The birthplace was often confused with the place they were living at the
time or had lived at one time. Some even put everyone in the same dwelling down as being
born in the same place. But, on the whole, it at least gives you somewhere to start.
The ages on the 1841 census were supposed to be rounded, but it wasn't always
consistent
20 = 20 to 24
30 = 30 to 34
35 = 35 to 39
but sometimes the actual age was recorded.
There were also groups of people who refused to give any information to the census
takers.
The 1871 and the 1891 census for Dolgellau are available online. I think I found them on
the Genuki website unfortunately it is not working today for some reason.
We haven't done a lot of research in Dolgellau, even though we do have family
connections there.
The parish records are probably your best bet to start searching. I don't know if
they have been transcribed or copies available for sale anywhere.
Doreen & John
Hamilton, Canada.