Looks good to me. At the moment, I don't think we need to mention feral cats - I doubt that it is common for feral cats to enter a house via a cat flap. On the whole cats are uncomfortable with entering another's territory, although I imagine it does happen occaisionally, especially if a feral cat learns that there might find food inside. If someone can find a useful reference on the subject we could re-add it. Mind you I did once find a wood pigeon tapping at my girlfriend's cat flap - which seemed particularly unwise.