"Other religion" is a vote for more faith schools
The massive increase in funding for faith schools in this country over the last decade has been justified entirely by the high proportion of people who picked a religion on the census. There are a lot of posts on here suggesting putting in "Scientist", "Atheist", "Pastafarian" or even "Smoker" in the other field, but bear in mind you'll be counted as a minority religion, and thus a vote for faith schools.
That's the reason for the BHAs campaign, and why it's important that atheists, agnostics, jedi and devout smokers all pick "No religion".