Oil groups Exillon Energy and Wood Group roared ahead, while sector peer Heritage Oil tops the fallers list.Exillon, the oil producer with assets in northern Russia and West Sibera, said that the estimate of proved (1P) reserves has increased by 40% to 112m barrels, while proved plus probable (2P) reserves are estimated to be 74% higher than previously estimated at 239m barrels.Oil services specialist Wood Group is to return $1.7bn to shareholders after it agreed to sell its Well Support division to US giant GE for $2.8bn cash.London Stock Exchange edged higher after migrating its main trading platform to a faster trading system over the week-end.Trading systems developer Fidessa was lower, as it kept up its tradition of paying a special dividend after it saw 10% growth in revenue and adjusted profit before tax in 2010. Brokers were divided over the results: RBS maintained its 'buy', as it expects market conditions to improve; while Peel Hunt kept its 'hold' as it downgraded 2011 and 2012 earnings forecasts by 2% and 6%, respectively.FTSE 250 - RisersExillon Energy (EXI) 394.90p +15.98%John Wood Group (WG.) 649.00p +13.36%Daejan Holdings (DJAN) 2,932.00p +4.90%JPMorgan Indian Inv Trust (JII) 429.40p +4.68%AZ Electronic Materials SA (WI) (AZEM) 326.80p +4.21%Mcbride (MCB) 143.90p +3.82%Homeserve (HSV) 478.60p +3.59%Devro (DVO) 236.00p +3.51%Pace (PIC) 225.40p +3.44%Croda International (CRDA) 1,522.00p +3.33%FTSE 250 - FallersHeritage Oil (HOIL) 297.70p -3.38%Imagination Technologies Group (IMG) 338.10p -3.26%Micro Focus International Plc (MCRO) 397.80p -2.64%Bellway (BWY) 662.00p -1.85%Brewin Dolphin Holdings (BRW) 163.00p -1.69%Computacenter (CCC) 412.60p -1.67%Punch Taverns (PUB) 68.80p -1.64%Close Brothers Group (CBG) 827.50p -1.61%Fidessa Group (FDSA) 1,673.00p -1.59%Persimmon (PSN) 437.80p -1.57%