Personally I wont be going to classes this time. I went to the NHS classes when I was pregnant with my son and found them to be a bit of a waste of time to be honest. Im not saying you shouldnt go, its very much a personal choice, but they didnt tell me anything I didnt already know or couldnt have found out by reading a book or looking it up on the net!
Basically they covered the changes in your body, signs of labour and what to do, then the actual process of labour such as how baby descends and what happens physically. The next class was all about pain relief during labour, what is available and how it affects you. Then it covered the birth and what happens after, delivering the placenta and onto recovery. Then the final class was a follow up one to discuss care of baby, how to bath, feed, change etc and a long bit about breastfeeding.
Maybe its just me, but I was a bit neurotic with my first and read every pregnancy book in sight and was constantly on the internet too. So I kinda got all the information I needed from there and was quite clued up before I went to the classes so found them a bit mundane and boring. Plus the one thing I was really interested in - relaxing and breathing during labour - wasnt covered at all so I just felt like I didnt gain anything from them. However, the one good thing I will say is that you do get to meet other mums and families around the same stage as you, so that is one bonus. I personally wont be going, but thats not to say they wont be useful for everybody, just depends how much research you have already done for yourself.