Parish Chest information for Welsh counties is mainly at the county
archives. In the case of Glamorgan, this is split between Glamorgan
Archives, at Cardiff (eg for Colwinston, Coity, Newcastle), and West
Glamorgan Record Archives at Swansea (eg Llangyfelach, Llandilo Talybont,
Neath). Some parish records were formerly at the National Library, but
have all (or almost all) been sent to the county archives. There is no
longer access to the physical registers at Glamorgan Archives; Glamorgan
Family History Society have indexed all Glamorgan parish records, and you
can see this index on-line at Cardiff. The index is linked to an electronic
image of the register. You can download the image onto a data stick free
of charge. I'm not sure what the arrangements are at W. Glam Archives.
The local record offices will also have whatever county court records may
have survived.
Other records which might be useful - for instance estate records, which I
have found particularly helpful for my farmer ancestors - may be at the
local archives or at Aberystwyth. If you type a parish name into the
Archive Wales search box, it will list the relevant records. "Colwinston"
for instance brings up 11 sets o records, nine at Glamorgan archives, one
at Gwent, and one at Neath Antiquarian Society.
You could try this for your other parishes - I think you will find that the
two Glamorgan Archives are much more useful than the National Library,
Anna