Thanks for your reply Wayne, it's good to know that other people bother to help the poor cats in the wild.

Yes, that polystyrene stuff really insulates, my husband suggested it. It's of course more important in cold countries.

I think the idea is good, because even an old lady could do it (they're often the ones who care the most, and the polystyrene is not heavy to carry)

One could also put a sort of roof on top, so the rain don't ruin the box - and so the cat can eat his food in the dry. Putting the box on some bricks would also avoid the cold from coming through the bottom.