'Shush - secret session for advancd thinkers'. Post-war planners have been told - sometimes rudely - that we've got to win the war first. We agree - absolutely. But we can't help feeling that if we'd looked ahead before the war there might not have been one. Take plastics, for instance; they're going to play as big a part in winning the peace as they are in winning the war, so we're going to publish a series of advertisements to show what plastics can and cannot do - just for the few who pre