Leading European exchanges remained higher midday buoyed by lower oil prices and a swathe of M&A news with Carrefour making solid gains after its results, dealers said. At 1.28 pm, the STOXX 50 was up 20.49 points at 3134.8 and the STOXX 600 was up 1.84 points at 286.66. Spreadbetting firm IG Index said the Dow is set to fall 8 points at the open. Lafarge added 2.86 pct, Holcim rose 1.79 pct and Hanson added 0.43 pct amid hopes the groups will benefit from the construction work in the US after the devastation from Hurricane Katrina. Saint Gobain, though, was up only 0.91 pct after the Financial Times said BPB PLC is considering gearing up its balance sheet to fend off an approach from the French group which yesterday formally launched a hostile 3.7 bln stg cash bid for the UK plasterboard group. Carrefour gained 2.18 pct after it reported interims at the top end of expectations. "A reassuring performance given the more than just difficult consumer environment," said Fideuram Wargny analysts.