What is English music? The freshness of a spring morning, or the chaotic bustle of Edwardian London? Michael Seal travels from the cherry blossom of John Foulds’ April - England to the glittering streets of Vaughan Williams’ A London Symphony – complete with buskers, fog and the chimes of Big Ben. And Lise Berthaud finds the dark heart of Walton’s smouldering Viola Concerto.