No, you're not, Starkers, but you have to boil down the story for dramatic purposes. You can't show everything, so some symbolic characters had to suffice, like Andy.
As for the politicians, yes, they aren't all morally bankrupt, but in the situation they found themselves in and with the enormous pressure when you sit at the Cabinet table I'm not so sure anyone would really speak up. The Home Secretary sort of did but as nobody followed suit she settled for saving her own kids and eventually spiralled down into suggesting to take the underachievers. This all seemed very realistic to me as one possible scenario. It doesn't mean it's the only possible outcome. But that was what the story was about.
It would be interesting to see the fall-out of this and how this played out in other countries since I assume that some wouldn't go along with this or couldn't due to the lack of infrastructure (e.g. China and India).