https://informatic.wiki/wiki/U....sing_a_Cat_Flap_in_B
You could consider installing a cat flap on the door made of upvc for those who want to allow your pet to go inside and out of the house without worrying that they'll leave behind unwanted "gifts". This is less expensive than replacing the entire door, and is easier to install. It is possible to set up a cat flap on your own uPVC doors however, it's an arduous task that can lead to costly mistakes. Easy to install It is essential to allow your pet or cat inside and out of your home. This will not only keep them safe as well