This postbox may be out of date with regard to collection times, depending how new the photo this post on Reddit is (https://www.reddit.com/r/london/comments/ms7zyx/this_tree_taking_over_again).  The plaque in the photo is dated 20/10/2020, whereas the collection times were added 29/12/2019 by https://www.openstreetmap.org/user/Martin%20Constantino%E2%80%93Bodin, so may have changed since then.

Should it be:
collection_times=Mo-Fr 16:30, Sa 12:00