"if I hack (not that I'd have a clue how to) into the Israeli defence force and told a load of Palestinians that they we're going to lob a load of cluster bombs in the general area of a Hamas leader. Will I be charged as i clearly have SAVED a lot of lives."
No you haven't. You've aided and abetted a terrorist. The computer misuse act will be the least of your worries, as you quite rightly board a plane for gitmo/wherever, never to be seen again.