Well my exhaust bung (for the lambda sensor hole) lasted all of a week, it's unscrewed itself and buggered off (I think I heard it tinkling down the road).
So I've had to find another bung and I've jubilee-clipped that in place to make double sure!!
If you've started using jubilee clips on the exhaust you might as well go all the way and use gun gum and wire coat hanger on other weak points along the exhaust. That should amuse the MOT man