Got to admit, it was just based on my perception of Christmas, rather than actual figures. But note that I am not talking about the numbers of people who are Christians, I am talking about the percentage of
Christmas that is Christian.
How many people went to church on Christmas day? What percentage of programmes on TV had a religious theme? What percentage of the decorations have a religious theme?
How much of their waking hours did the average person spend thinking about Jesus or just praying? I suspect the figure is rather less than 5% - but I accept I have no figures to back that up.
This is not the same, but worth discussing anyway.
There is an issue here about what counts as Christian. Is someone who goes to church for weddings, Christenings and funerals, but does not give religion a thought outside of that a Christian? Plenty of people put Christian on forms as a default, without actually being religious. Your census shows a huge leap for "no religion" from 25.2 to 37.2 in ten years, and I would suggest a part of that is people deciding "no religion" is a better label, rather than a huge change in beliefs.
Bear in mind UK church membership is steadily declining. The latest figure I found is 10.3% ten years ago (
here), I would guess it is nearer to 5% by now. I appreciate there are plenty of Christians who do not attend church, but I think this also indicates the figure of 46.2% for Christians is a serious over-estimate.