cornish strormrider - like many before you, you entirely miss the point of nuclear deterrence. You are of course correct that once we have to use them, we have already lost, but the point is it is a potential enemy's belief that we will use them which prevents him using his own weapons. Throughout the Cold War, the prospect of mutually assured destruction kept the peace.
I want us to live in peace with our neighbours too, but there is an old saying - "good fences make good neighbours" and our nuclear fence should remain for that reason