I was told about the NCT classes and really wanted to do them but the course that I was given information about was very expensive and quite far away from me.
So I've decided not to do them, due to the fact that I don't drive and have to work early the next day. So I know I am going to be more exhausted if I do them and cost for travel will be quite a bit too.
Have you spoken to your midwife as if you are unsure about what to do she can give you some advice.
I spoke to mine recently and she gave me a number for the normal NHS one and other private ones which are just as good as NCT ones but nearer and slightly cheaper.
Sorry if I've not been much help.
If you still decide to do the NCT course I'd say do the 8 week one if you can get there easy enough as the weekend one probably will be a bit intense and the course will probably start nearer the time that you are due and if you are a bit early you might not of have had the chance to do the course. Where with the 8 week one even if you go into labour early you might of had a few classes to begin with that will still help you.
Let me know what you decide, best of luck x