Imagination Technologies is the worst performer Wednesday despite continuing to see growing demand for its graphics chip technology, though its Digital Audio Broadcasting division, PURE, is finding things a bit tougher. The group expects the volume of chips shipped in the second half of the financial year to comfortably exceed the 107m shipped in the first half.Adam Fowle, chief executive of Mitchells & Butlers, is to leave the pub owner by mutual consent after two years in the job, sending shares lower.Heading the other way is baker shops chain Greggs, which reported record numbers during 2010, pushing profits up almost 8%.Witan Investment Trust is unwanted despite outperforming its benchmark index in 2010. Retailers Halfords and Home Retail Group, which owns the Argos and Homebase stores, are also in the red.FTSE 250 - RisersHansen Transmissions International NV (DI) (HSN) 49.17p +4.82%Gem Diamonds Ltd. (DI) (GEMD) 259.90p +4.80%Bodycote (BOY) 319.20p +4.14%AZ Electronic Materials SA (WI) (AZEM) 267.50p +3.68%Catlin Group Ltd. (CGL) 346.20p +3.65%Heritage Oil (HOIL) 295.00p +3.44%ITE Group (ITE) 244.00p +3.39%Carpetright (CPR) 728.00p +3.26%Computacenter (CCC) 424.40p +3.26%Brown (N.) Group (BWNG) 260.60p +3.21%FTSE 250 - FallersImagination Technologies Group (IMG) 435.00p -5.97%Thomas Cook Group (TCG) 164.20p -3.92%Mitchells & Butlers (MAB) 287.80p -3.91%Cookson Group (CKSN) 624.50p -3.78%Temple Bar Inv Trust (TMPL) 833.00p -3.70%SVG Capital (SVI) 226.30p -3.37%Cable & Wireless Communications (CWC) 47.40p -3.34%Law Debenture Corp. (LWDB) 322.30p -3.33%Halfords Group (HFD) 358.50p -3.26%Aveva Group (AVV) 1,594.00p -3.22%