I did lots of reading before hand but Im still really glad I did the NCT classes, met some lovely people and even though I knew a lot of it already, talking about things I think has prepared my mind more. There has also been stuff I've read and been told by others thats all conradicted each other, and the classes cleared that up. And its been great for OH too. We've been out to lunch as a big group, and the husbands have all met for drinks. Talked about emotional side of things aswell as the givin birth and drugs etc, Talked about parents, in laws, guests once baby here etc, what OH should do when we are in labour and act strangely haha.
So you'll be fine without, as many have already said, but I do think they are a great benefit if you can afford to go.