David Cameron has recently claimed that the UK is a 'Christian country' and has said that he will act as a 'giant Dyno-Rod' for Christian organisations here (implicitly equating secularists with sewage). This has attracted considerable criticism, for obvious reasons.
England is a Christian nation in a legal sense. The other constituent countries of the UK have a different set of rules about religion, but the Church of England is the established church of England with the Queen as its head, so in legal terms Cameron is nearly correct. In other respects, though, the UK isn't a Christian nation; some polls show that the population now has a non-Christian majority (made up of non-religious people and people of other religions), and nearly all of our laws and mores derive from secular reasoning, not Christian tradition.
This is apparently controversial in some quarters, but it shouldn't be: England was majority Christian for a thousand years by the time slavery was abolished, and it took even longer for the death penalty to be gotten rid of. Such moral leaps did not derive primarily from Christian tradition. We simply don't depend on the Bible in any way for our morals and precepts, and I'd say we're doing quite well without it.
Given that even self-proclaimed Christians in the UK rarely go to church and that non-Christians are in a majority, and that the mores of all groups come from reason and ethical discussion more than tradition and theological mumbo-jumbo, it hardly makes sense to refer to the UK as 'a Christian country'.
It is obviously wrong to have an established church (or a monarch, for that matter). How can a government take such a stand on metaphysics or decide for the population at large whether there is or is not a god? It's clearly a stupid idea, and clearly all of earth's nations should have secular governments by default. Saying that the UK is still a 'Christian country' only serves to highlight how impervious to obvious notions the English political establishment is. The sooner we ditch the church and monarchy the better off we'll be, and whether Britain is or is not currently a Christian country is moot; the point is that it shouldn't be.
Naturally, I'll be doing my best to vote Cameron out in the next election, but that effort has already been hampered by the failed referendum on reforming British elections a few years ago - another result of the glacial rate of political reform in the UK and the sheer impossibility of introducing new and better ideas into the country's archaic and calcified system.