Investors have an appetite for shares in Premier Foods after JP Morgan upgraded its rating on the stock.The company which makes Branston Pickle and cakes for Cadbury, faces a tough 2010, reckons the broker, but based on recent underperformance of the shares the US broker has upgraded its rating on the stock.JPMorgan (JPM) now rates the shares as 'neutral', having previously advised clients to be underweight in the stock. The upgrade is on valuation grounds, following the 23% price fall in the stock since mid-October, which has brought the share price below JPM's price target of 36p.Among other risers is Shaftesbury, the property company with assets in London's Chinatown and Covent Garden, which said the economy in London's West End remains resilient.'Demand for our shops, restaurants and residential accommodation has remained healthy and our rental income continues to grow strongly,' said John Manser, Shaftesbury's chairman.Pub group and brewer Greene King froths higher after it shrugged off the worst of the downturn over the last six months thanks to a strong performance from its Scottish arm Belhaven.Also higher is private equity investment firm Electra, which said its investment portfolio is 'in good shape' despite a tough year.FTSE 250 - RisersPremier Foods (PFD) 35.03p +6.77%Yell Group (YELL) 41.27p +6.48%Shaftesbury (SHB) 391.70p +6.27%Persimmon (PSN) 438.40p +6.00%Greene King (GNK) 422.50p +5.28%Inchcape (INCH) 29.22p +5.15%Electra Private Equity (ELTA) 1,206.00p +4.96%Barratt Developments (BDEV) 124.00p +4.91%BlueBay Asset Management (BBAY) 330.00p +4.76%Kier Group (KIE) 946.00p +4.76%FTSE 250 - FallersGrainger (GRI) 133.90p -7.25%Salamander Energy (SMDR) 256.50p -5.84%Imagination Technologies (IMG) 206.20p -2.23%QinetiQ Group (QQ.) 153.80p -2.10%Talvivaara Mining Company (TALV) 401.50p -2.07%Genus (GNS) 603.00p -1.95%St. Modwen Properties (SMP) 208.00p -1.79%Robert Wiseman (RWD) 482.80p -1.47%F&C Commercial Property Trust (FCPT) 85.25p -1.45%Bodycote (BOY) 155.20p -1.21%