Given LulzSec seems to post their hacks on twitter, that there's no way of validating who posted the PasteBin item and that the Office of National Statistics hasn't reported the loss, its probably best to wait and see something a little more convincing.
I wrote the article and have been trying to trace the authenticity of the release. I am still waiting to hear back from the Office of National Statistics, which at the time were unaware of who LulzSec even were. I contacted them a little over two hours ago, I haven't received a response, yet.
It may take them a while to figure out what a "computer" is and how it might be "hacked". You could be waiting some time :)
ahem.