On Fri, 25 Apr 2008 23:22:30 +0100, "Angela"
wrote:

1. As it's a cavity wall do cats have a problem going through a tunnel?

Yes - they won't go through a cat flap sized tunnel. They will go
through one which is a bit bigger so they can stand as they come
through - so about 3-4 bricks high.

2. The actual door seems to be on the inside leaving the tunnel exposed to
the elements (or have I got that wrong?). What's stopping it filling with
rain and allowing water to seep into the cavity wall?

The cavity wall is designed to be wet - but why not put the cat door
on the outside?

Knocking holes in walls is quite a drastic thing to do so I don't really
want to do it unless it really is the right thing............though I'm not
sure what else I will do if it isn't!!

It's actually easier than modifying the door and simpler to remove if
you ever need to.