"No religious affiliation" up 6.3m from 2001, christianity down 4.1m from 2001.
"The number of residents who stated that their religion was Christian in 2011 was fewer than in 2001. The size of this group decreased 13 percentage points to 59 per cent (33.2 million) in 2011 from 72 per cent (37.3 million) in 2001. The size of the group who stated that they had no religious affiliation increased by 10 percentage points from 15 per cent (7.7 million) in 2001 to 25 per cent (14.1 million) in 2011." - www.ons.gov.uk
Survey of religious belief in the UK
One interesting finding "only 54% of the population say they are Christian, and of these, only 35% could correctly identify the first book of the New Testament."
What is clear is that most people wh call themselves Christian are not Christians, because they do not believe in the teachings of Christianity.