The purpose of ringing the bells down is to make them safe - hanging with the bells at the bottom of the wheel. The ringing room is on the ground floor of the church, so it's really important to make sure that if someone were to grab a rope by accident nothing bad would happen to them!
+Timothy Garrison It's very unlikely. It's a little sad that the clapper is hidden in the top-down view, however, if the bell were up wrong you'd be able to see the clapper in the side-on view of the tenor (top right image). I appreciate it's not very clear, but I'm pretty sure the clapper (also painted blue) is not visible there.
