I did the post natal class & I have to say that it was a bit of a waste of time, the timing wasn't great at 10am as it clashed with feeds etc & it wasn't what I was expecting.
I would see how your ante natal class goes & what your group is like, it's a bit of a lottery & you may find that you don't really have anything in common with many of them other than having a baby within a few weeks of each other.
NCT antenatal classes focus on the birth & don't prepare you for after the birth. There are some great books again so do read up!
I saw my NCT group 1x a week or so for the 1st 7 months or so but tailed off after I went back to work & now I rarely see any of them.
I met other mummies through Tin Pan Annie, Sing & Sign, baby swimming etc & still see them now so NCT isn't the only way to make new friends.
Good luck