LONDON — The one place Alan Ayckbourn has yet to conquer is the United States. Mr. Ayckbourn, though, is not surprised. "A lot of people in America thought I was another Neil Simon and tried to play my [productions] as such," he says, "and you can't play them like Neil Simon's; they are different beasts."Americans and the English, he believes, are the widest apart in certain fundamental ways, when compared with many other nationalities, because "we don't accept each other as foreigners," he observes, "and so only partially recognize what we're actually talking about.... [In Britain], for example, we have a whole code of half-things we say, which mean something else. And if you're not attuned to that, you don't really know what people are communicating. It's a terrible generalization, but Americans, to my mind, tend to speak much more plainly and directly. Whereas, my plays use the coded language of the English. It's like the difference between the American game of pool and our snooker: Most of the snooker [points] come off the cushions. You rarely make a direct shot."