The snow on our Barn Owl box looked undisturbed by anything large , but perhaps
some smaller birds sheltered in there when the weather was really bad.
All the sticks and debris left by previous occupants (not Barn Owls) have been cleared by Roger's ornithologist friend. Perhaps the pair of Barn Owls that were hunting over the wood on Monday will be tempted to make this their home, although they might be put off by at least two people aiming cameras at them!
For those people who want to encourage more birds to nest in their garden, this page on the BTO site might be useful.