We have a serving hatch which we love. However, the kitchen is unheated and it's a bit draughty now the weather is turning colder. We've put up a basic roller blind for now, which has helped a bit, but the cats have now worked out that they can push it and get into the living room during the day (meaning they've locked themselves in a couple of times this week - once with a dead mouse). What would you suggest putting up instead? We thought maybe shutters but we don't know where to start.