Rail and bus operator Go-Ahead is among the best performers Friday after it announced that it will continue to operate the Southeastern rail franchise in Kent until 2014, through its joint venture with French transport group Keolis.London and south-east housebuilder Berkeley Group continues to benefit from the region's position as a pocket of strength in an otherwise gloomy housing market. The group said it anticipates earnings coming in at the high end of expectations for the year ended 30 April.Drax is making gains after broker Matrix said it should benefit from higher gas and electricity prices. Prices are expected to rise as a result of nuclear power plant closures in Germany and Japan following the ongoing nuclear crisis in the latter country.Engineering firm Aveva is wanted, bucking its recent trend, after Panmure Gordon said that any further weakness in the shares should create a buying opportunity. The share price has fallen around 8% in the last week.William Hill is higher after being granted an extension to the injunction preventing Playtech from selling its stake in William Hill Online.Fund manager Jupiter is the worst performing stock by some way despite enjoying a profit burst in 2010. Pre-tax profit came in at £42.4m compared with £7.2m in 2009. But investors were underwhelmed after the chief executive warned of "significant short term volatility" in the markets.FTSE 250 - RisersSalamander Energy (SMDR) 282.00p +6.94%Go-Ahead Group (GOG) 1,400.00p +5.34%Lancashire Holdings (LRE) 597.00p +5.01%Rentokil Initial (RTO) 88.95p +4.59%COLT Group SA (COLT) 149.50p +4.11%Britvic (BVIC) 388.70p +4.07%Imagination Technologies Group (IMG) 450.50p +3.95%International Personal Finance (IPF) 322.20p +3.94%Telecity Group (TCY) 490.50p +3.90%Exillon Energy (EXI) 402.40p +3.79%FTSE 250 - FallersJupiter Fund Management (JUP) 300.30p -5.66%Daejan Holdings (DJAN) 2,674.00p -2.73%Grainger (GRI) 102.90p -2.19%Cable & Wireless Communications (CWC) 47.87p -1.74%Micro Focus International Plc (MCRO) 297.90p -1.46%Domino Printing Sciences (DNO) 636.00p -1.40%Aegis Group (AGS) 136.70p -1.37%Ocado Group (OCDO) 220.00p -1.30%Pace (PIC) 163.70p -1.27%Helical Bar (HLCL) 277.50p -1.25%