Private Parking Companies! Don't Pay 'Fines'

Giblets

Again I think this depends on who does it, if its the council...cough up.
A private firm, however, is another matter, i have heard people meerly being cautioned damaging a clamp. Have also heard that a good way is to let down your tyre, and you can, depending on the type of clamp, and you tyre ( am guessing low profile (sports tyres) are a different matter) lever it over your tyre and release it ( and replace it with your spare until you can pump it up).

Of course they would need evidence that you damaged their property.