Helen, how does the 4 way locking one work?
We have only ever had Jameson coming in and out of ours, which is great as the door which his flap is installed on backs out on our garden and then the shrublands so we thought all other cats/foxes would use it (esp as Jamesons food bowls are by the flap).
Only problem with cats having free access is the amount of 'lovely' presents you recieve (at any given time of the day). Be prepared to wake up with birds flapping around in your bedroom, or worse, a halfdead mouse on your chest!