Tepid as a glass of English beer, long-winded as an American used-car salesman, this ""survival guide"" fails both as travel information and as humor. Walmsley, an American-born broadcaster and journalist who has lived in London for the past 15 years, offers her readers such ""insider"" revelations as the fact that ""English muffins"" are unknown to our transatlantic cousins, and that what Americans call ""the first floor"" the Brits consider ""the ground floor."" Americans, she also informs the uninstructed, talk more about sex than the English seem to--hardly the sort of insight that leaves the reader agog with wonder. The familiarity of much of the British information might be less of a handicap if it were hot coupled with equal portions of misinformation about life in America. Or if the author were able to present her perceptions, accurate or inaccurate, from a fresh viewpoint. Were she able to approach her subject from an unexpected quarter, to sharpen it with a satiric edge, there might be possibilities in her theme. Another of the problems she faces here is that she attempts to mock British attitudes for her American readers while skewering American idiosyncracies for her English fans, Unfortunately, you cannot lie down with both the lion and the eagle, it seems. Just as damaging is Walmsley's writing itself--flat, rambling, repetitious. There is more than a little truth in the bromide ""Brevity is the soul of wit."" The text is interspersed with a series of cartoons by artist Gray Jolliffe. Described as ""acerbic,"" ""bland?' comes closer to the mark.