Heritage Oil is wanted after reports in the FT indicated the company has rejected an informal offer of 425p per share from an Abu Dhabi based investor. "This would represent a 47% premium to yesterday's close and a 25% premium to our current target price of 341p," said resources specialist Westhouse Securities. "It would also add another potential suitor pursuing Heritage, after weeks of speculation regarding interest from BG Group," the broker added.Sector peer Exillon Energy, the oil producer with assets in northern Russia and West Siberia, is the worst performer today.Firmly higher is construction products supplier SIG, which posted an underlying pre-tax profit of £62.5m for the period, up 3.1% from the previous year. Revenues slipped 2% to £2.67bn.Greggs isn't too far behind after broker UBS reiterated its 'buy' rating on the bakery chain, expecting its shop roll-out and cost control plans to continue into 2011. Broker finnCap upgraded the group from 'hold' to 'buy'.Estate agent Savills is in the red despite revenues growing 21% to £677m in 2010. Underlying pre-tax profit soared 88% to £47.3m.FTSE 250 - RisersHeritage Oil (HOIL) 314.80p +8.66%SIG (SHI) 131.50p +8.59%Greggs (GRG) 504.50p +8.19%Gem Diamonds Ltd. (DI) (GEMD) 270.00p +8.00%Domino Printing Sciences (DNO) 655.00p +7.11%Morgan Crucible Co (MGCR) 294.30p +6.59%Lancashire Holdings (LRE) 567.00p +6.48%Taylor Wimpey (TW.) 39.99p +5.88%Persimmon (PSN) 448.80p +5.80%John Wood Group (WG.) 623.00p +5.68%FTSE 250 - FallersExillon Energy (EXI) 395.20p -3.61%Aveva Group (AVV) 1,523.00p -3.55%F&C Asset Management (FCAM) 76.90p -2.66%Aberdeen Asset Management (ADN) 197.90p -2.46%Renishaw (RSW) 1,521.00p -2.31%CSR (CSR) 367.40p -1.50%Ladbrokes (LAD) 127.30p -1.39%Salamander Energy (SMDR) 271.90p -1.34%CPP Group (CPP) 307.20p -1.16%Savills (SVS) 370.00p -1.07%