As Helloworld said, generally there is a left-leaning tendency, although the green party isn't really as strong as you think. In general, there can be a much stronger Labour support. However, there is also a fair bit of apathy to party politics, so the left-leaning is sometimes a lot more vague and theoretical unfortunately.
I really have no idea about the non-religious aspect. From what I could gather, I think there's a fair bit of religion knocking about, they just don't feel the need to advertise. Although I say that because my uni at least has a Christian Soc and a Muslim Soc, as well as possibly others. I guess the existence of these societies can make them a little insular, which is probably why students give off the appearance of being non-religious.