I think it's a real shame that the classes in your area are so expensive. Our branch has kept them below £100 for a long time (8 x 2 hour sessions, plus an extra session on breastfeeding) and £200 seems exorbitant.
We did a longer course, but I have also sat in on a 2 day one, and I would echo what various people have said about it being too short a time to absorb all the info. Bear in mind that you may be quite heavily pregnant by then, feeling tired, and with all those pregnancy hormones making it difficult to remember lots of stuff!!
As an NCT local representative (responsible for coordinating coffee mornings and other social events), I would really encourage you to give the bumps and babes sessions in your area a go after the birth, if you eventually decide that the classes themselves are too expensive. You don't have to be a member to attend, and you will find people with babies of a similar age. Yes, a lot of people bond well with their NCT antenatal class, but as this thread has shown, a lot do not. You may well find you meet some really great friends there. If you ring the host in advance, and say that you really want to meet other mums, and that you haven't got a good antenatal group to fall back on, they may well be able to introduce you to people specifically.
The other source of support would be postnatal classes that are run by most health authorities. These tend to deal with things like first aid, play and development etc. but as they are often a rolling programme, you tend to meet other parents with children about the same age as you.
We also did NHS classes, and whilst they were good (and a great complement to the NCT ones - being more practical) they were packed (24 couples!!). The age range was huge and meant we couldn't get to know people. Everyone was at a different stage of pregnancy too, so people were coming and going throughout the course.
I would definitely do the NHS ones (they're free), and then go along to some of the bumps and babes sessions before the birth, so you get to meet other mums who've just had their babies. They will hopefully be less dismissive of your questions than some longer-established mums can be.