That's a great observation. IF there was a way to boil down the language to a sound bite, it would stick.
"Persuant to Iran's tactical statements on the Iraq Campaign, connected with the act of war in capturing our sailors, they have become an enemy state in the War on Terror. Iran will regret it's actions."
Not short, but how's this?
"By demanding the immediate withdrawal of our forces from Iraq, as a condition of release of 15 British maritime hostages, Iran has identified its status as an enemy state combatant in the War on Iraq. To that end, the United Kingdom demands either immediate release or full adherence to the Geneva Convention regarding the protection and providence due uniformed prisoners of war. If these protocol are not observed in full, Great Britain reserves the privilege to invoke it's right to self defense and employ whatever means necessary to secure the release of said prisoners, up to and including decisive military force."