Fdit Cat Flap Door for Cats Dogs Pet, Large Cat Flap Door for Windows Sliding Glass Doors With 4 Locking Possibilities (Round Transparent) : Amazon.co.uk: Pet Supplies
DIY Fitting of Cat Flaps and Dog Doors
The prefect Cat Flap for a sliding patio door.Cat flap Fitter advice blog.
Installing flaps in double glazing glass & UPVC patio doors
The Cat Door Alternative That Saves You Time & Money - LockLatch
Cat Flaps in Glass — Samuel Charles Glass & Glazing Southampton