There are several different ways to accomplish this but at present we do not have a one button press to unpublish. Your best bet would be to rename your public folder in your hosting space which will cause you site to display a "forbidden" error. You can also simply rename your index page which will give visitors that go to yourdomain.co.uk a "forbidden" error but keep in mind that they can still get to other links provided they know the correct file or folder names to access them directly.
