THERE isn’t a musical ensemble more fitting and attuned to leading a concert commemorating the October 4 1936 Battle of Cable Street than the east London-based Grand Union Orchestra. Composed of local musicians from heritages as far apart as China and Chile, the Caribbean and Bangladesh, South Africa and Russia, Australia and the Ivory Coast, the sheer cosmopolitan power of these universal troubadours  exposes out loud and in melody Oswald Mosley’s inheritor Nigel Farage, and the masked men of Dover and Portsmouth, as a scourge of humanity.