12.5.3<br> On the second day following the day notice was posted by first class post to the address first applied to the Contract or any address from time to time provided to one party by the other in substitution thereof.</p> <p>12.6<br> In the event any provision of the Contract or these Terms and Conditions is held to be invalid or unenforceable, the affected provision shall be deemed amended to the extent necessary to render it enforceable.