Dave
If your interest is in Cardiff I would recomend the Glamorgan Record Office
in Cardiff for census and parish records rather than the National Library.
It is very easy at Cardiff. Parish Registers are on open shelves so can be
picked up as you want them. Census is on microfilm or fiche. You need to
book a reader for that.
My experience of Nat Lib is a few years old but I did not find it user
friendly. You have to order what you want a little at a time and then wait
for it.
At the Record Office you can move from parish register to parish register
very easily.
The Record Office also has the GRO Registration Indexes on fiche and the
Probate Indexes for Llandaff (covering Cardiff area). Also the Cardiff
Rgister Office where you can get copies of Birth, Marriage & Death
certificates is quite close to the Record Office.
Regards
Bob Sanders
Cardiff