Iron ore producer Ferrexpo is leading the risers in the FTSE 250 as metal prices advance on hopes that China's decision to allow the yuan more flexibility after a two-year peg against the dollar, will reinvigorate the east Asian powerhouse's economy.Finnish nickel and zinc miner Talvivaara Mining is also going well as us Aquarius Platinum, which mines for the precious metal in South Africa.Lamprell is going strong again having posted good gains on Friday when the engineering services group announced a $129m deal to construct wind turbine installation vessel.FTSE 250 - RisersFerrexpo (FXPO) 294.80p +7.36%Dana Petroleum (DNX) 1,216.00p +5.28%Lamprell (LAM) 239.50p +5.23%Cookson Group (CKSN) 484.80p +5.00%International Personal Finance (IPF) 221.70p +4.92%Aquarius Platinum Ltd. (AQP) 404.90p +4.65%John Wood Group (WG.) 334.20p +4.01%GKN (GKN) 134.20p +3.87%Wellstream Holdings (WSM) 563.50p +3.78%Talvivaara Mining Company (TALV) 405.00p +3.45%FTSE 250 - FallersFidessa (FDSA) 1,381.00p -4.50%Daejan Holdings (DJAN) 2,449.00p -3.05%Dignity (DTY) 637.00p -2.52%Hansteen Holdings (HSTN) 67.05p -2.33%Drax Group (DRX) 379.60p -2.32%PZ Cussons (PZC) 320.50p -2.29%Weir Group (WEIR) 1,144.00p -1.72%Northumbrian Water Group (NWG) 299.10p -1.71%Kesa Electricals (KESA) 115.40p -1.54%Game Group (GMG) 81.80p -1.45%