It's worth finding out what exactly your NHS antenatal classes will be like - we were offered drop in sessions at a large london hospital that were run on a rolling basis so no guarantees of seeing the same participants again. Also, there were upwards of 30 couples there so not an ideal place to make friends.
For nct might be worth looking into who will be running the course and what sort of area the participants are from. again - we did the central london ones and they attracted people from across london so not so good for making long term friends.
however, the person running them was fantastic, she did tell us that it would hurt like fuck and then some but gave a whole raft of different things that might help to deal with the pain. Including drugs, yoga, breathing, positions, even stuff that she said hadn't worked for her but had worked for others so still included.
one of the participants had pre eclamsia before the last session and was in hospital being monitored and then going to be induced, she got her husband to see her and went through a whole load of things with him relating to the induction and ways to help his wife and what could be expected, what to ask and when, which they both found really useful and supportive at what had become a very scary time for them.
The other thing to do is to see if there are any independent midwives near to you and see if they run sessions, or if you have several friends who are also pregnant, see if you could negotiate for them to run a course for you based on what you need to know, might work out much cheaper, espeically if you were able to host it in one of your houses rather than need to have a room rental element in the price IYSWIM.