UK stocks erased early gains as Greek concerns and a lack of economic data stoked investor uncertainty. Sector-wise, retailers and insurers delivered the biggest drag, while energy, mining and tech stocks provided a welcome boost.As of 2:00, the FTSE 250 was trading flat, just 9 points lower at 18,011 points.Engineering software group Aveva topped the risers on weekend reports that it could be an acquisition target of Schneider Electric, General Electric and Emerson Electric.Online gaming group Bwin.Party Digital Entertainment jumped after confirming it has received a cash and shares bid from sector peer 888 Holdings.Cranswick brought home the bacon as its annual revenues hit £1bn for the first time, as sausage, burger and bacon sales offset weaker results from fresh pork. Exports outside Europe grew 23% as the meat provider broke into Asian, African and Australian markets.Tullow Oil was making gains as conflict in Iraq and Yemen buoyed oil prices.Outsourcer Mitie was climbing despite posting flat full operating profits, as its performance was capped by local government cuts which weighed on demand for its homecare and social housing business.Satellites operator Inmarsat dipped after news of a delay in the launch of its third Global Xpress satellite. RisersAveva Group (AVV) 2,014.00p +9.75%Bwin.party Digital Entertainment (BPTY) 107.70p +8.30%Kier Group (KIE) 1,387.00p +4.75%AL Noor Hospitals Group (ANH) 878.00p +4.15%Hunting (HTG) 615.50p +3.36%Mitie Group (MTO) 296.90p +3.20%Bovis Homes Group (BVS) 1,071.00p +2.39%Imagination Technologies Group (IMG) 207.40p +2.22%Rotork (ROR) 257.00p +2.02%Wood Group (John) (WG.) 710.50p +1.94%FallersThomas Cook Group (TCG) 155.60p -3.53%Nostrum Oil & Gas (NOG) 553.50p -3.40%Fidessa Group (FDSA) 2,265.00p -3.04%COLT Group SA (COLT) 150.30p -3.03%Premier Oil (PMO) 172.10p -2.88%Inmarsat (ISAT) 967.00p -2.86%Diploma (DPLM) 791.00p -2.41%Essentra (ESNT) 982.50p -2.34%SIG (SHI) 200.00p -2.20%Petra Diamonds Ltd.(DI) (PDL) 174.70p -2.18%