Hi Smicha
I have just finished mine, so I'll give you my opinion for what it's worth. We did an NCT course, which consisted of 6 sessions and had 2 free 3 hour NHS sessions - one on birth preparation and one on breastfeeding.
I wouldn't say any of them covered anything I didn't already know, but that's because I've been on mumsnet a lot, reading books, have a phone app etc, so have already got my information from there. The NHS covered the same content as NCT, but with NCT there were more activities based around the info - so rather than sitting and listening to someone talking about it, there were activities to do - some of which were a bit crap, but others that were good just because they got you all chatting about things.
NCT goes on a bit about the "natural birth" thing and you having control over your birth etc, whereas NHS is more about the practicalities, which I prefer in one sense, but it was also good to be made more aware of the fact that you could question your midwife more etc.
The NHS classes were good and informative and told you everything you needed to know. The advantage of the NCT was that it got us in the "baby zone" much more, because it was spread out over a longer period and the way it was delivered initiated more chat between me and my DH and us and other couples. We had quite a nice group for NCT and we are arranging to meet up again later, whereas I didn't really meet anyone through the NHS ones as it was a much larger group of people, there was no group work and it wasn't the same people at the two classes.
It was definitely worth doing the NHS birth preparation one as that also included specific info about the hospital we're going to and a tour of the delivery suite etc, which obviously NCT doesn't cover.
NCT was good, but it cost us over £300 and I'm not sure if it was that good as content was covered in the NHS ones. But lots of people talk about the value of NCT giving you a support network etc - it remains to be seen if this will be the case for us, but I can see the sense in it.
Hope that helps!