** Go-Ahead up 3 pct, on track for biggest one-daypct gain since June & among top FTSE 250 risers asNomura upgrades to "buy" vs "neutral"
** Co has most attractive mkt exposure in sector, Nomurasays, with 37% of FY16E EBITA from UK Regional Bus, 31% fromLondon Bus & 32% from UK Rail
** National Express, which Nomura cuts to "reduce"vs "neutral", 3rd-top UK midcap faller; broker has concerns onUS School Bus (should account for 32% of co's FY16E EBITA) - oneof the least attractive markets
** HSBC also cuts rating on National Express, to "hold" vs"overweight"
** Firstgroup, which Nomura says has worstsub-sector exposure (37% of group EBITA from US School Bus),down 0.5 pct
** But broker likes Stagecoach's operations; strongposition in London Bus, exceptional UK Regional Bus margins(albeit with attached legislative risk) & burgeoning UK Railreturns; stock up 0.5 pct (RM: tricia.wright1.thomsonreuters.com@reuters.net)