Antenatal classes

I think I must be the only 20 week pregnant woman that hasn't booked her classes because I tried today and found everything full! I'm stressing out just a bit now.. Birthcare have a 6 hour condensed class 2 weeks before I'm due and I am wondering if anyone has done this before and whether it is useful enough? Is 2 weeks before due cutting it too close?

If anyone has suggestions of other places I could try that would be great, I've tried mama maternity, birthcare, parents centre. I live on the shore but wouldn't mind driving anywhere in Auckland.