LONDON (REUTERS).- A group of talented and ambitious young artists join forces, determined to stir up the art establishment which they see as sentimental, stodgy and distant from reality. A familiar story? Perhaps not. The artists in question are not the French Impressionists, but an iconoclastic group that emerged in the Scottish city of Glasgow in the late 1870s to become the most daring and original painters in Britain at the time. The Royal Academy of Arts is hosting the first major London exhibition for more than 40 years celebrating the achievements of the group, known as the Glasgow Boys. More than 80 oils, watercolors and pastels by such artists as James Guthrie, George Henry, E.A. Hornel, John Lavery, Arthur Melville and James Paterson have been assembled from