Atheists are now hugely in the majority. 48.5% of Brits identify as having no religion (43.8% Christian). That's up from 25% in 2011. Hurrah! And by the way, I don't actually believe those statistics; change doesn't happen that fast. My guess is that these two figures were arrived at using different methodologies and definitions. Still, it's looking good!
Now we need to deconvert the others? No, we don't. All we need to do is wait until they do it for themselves.