Hmmm I'm in two minds about this.
My experience of NCT, is that although there is an underlying ethos of natural childbirth, the teachers will also try to tailor the course to any individual needs within the group. eg if a woman has had a previous section, then this may well be more of a focus than in another group, where they haven't.
The bottom line is, the vast majority of births have the potential to be natural. I assume Kirstie Allsop must be one of the minority who cannot give birth naturally, but we have to remember that's a minority. Even where a woman needs a CSection for a specific birth with one of her children, it doesn't mean it will be medically necessary for all (eg, I needed a Csection for dc2, but I had dc1 and 3 naturally).
We have to remember that the safest way, statistically, for a woman to deliver her baby is naturally. Of course there will be exceptions to that (as with my dc2) but its a general rule that holds true. Many CSections are carried out during a labour which could have had a natural outcome, but the cascade of intervention - perhaps the mother not being well supported enough, or given a range of natural pain relief options, or has an epidural and the labour is less effective - means a CS is the result.
I think the NCT are brilliant, and I don't believe they are in the business of trying to make anyone feel guilty - but I do think people need to be aware of what they are buying into. eg when a friend of mine, who was quite upfront about not being bothered by natural birth, and wanted "all the drugs going" asked me about NCT, I said that frankly, I would have felt it wasn't good value for money if I was sure I wanted a very medicalised birth. The emphasis is very much on breathing, relaxation, and natural methods, and it probably isn't best value if you're not someone who chooses that. (And yes, before anyone points it out, I know not everyone has the type of birth that they planned, but some women do decide they want medical intervention. I know quite a number who have specifically booked into hospitals where epidurals are available and routinely given, because thats what the woman wants.
So, all in all, I think the NCT are great, and I think a lot of this 'guilt' over CSections is misplaced, and isn't necessarily anyone's fault. I have certainly never, in real life, heard anyone call anyone else a failure for having a CSection. I have, on the other hand, come across some women who wish for themself that their labour had not been so medicalised.