Weakness in the pound has given investors in directories group Yell something to shout about. The shares are up 20% after revenue in the three months to 30 June rose 1.5% to £475.3m from £468.4m a year earlier. On a constant currency basis, however, revenue dipped 10.4%.Shares in Tate & Lyle bounded ahead as the sugar and sweetener group reported first quarter underlying profits were ahead of expectations.Online gaming titan PartyGaming is another gainer after it beefed up its bingo offering with the acquisition of Cashcade, owner of some of the UK's leading bingo web sites.Northumbrian Water is one of the water companies to fall back after the water regulator Ofwat outlined proposals on pricing over the next five years that were less generous than they hoped.FTSE 250 - RisersYell Group (YELL) 27.25p +19.78%IMI (IMI) 320.75p +9.28%Tate & Lyle (TATE) 340.25p +9.23%Rightmove (RMV) 422.75p +6.22%PartyGaming (PRTY) 249.00p +6.18%PV Crystalox Solar (PVCS) 83.25p +6.05%Barratt Developments (BDEV) 188.75p +5.89%DS Smith (SMDS) 74.00p +5.71%Wellstream Holdings (WSM) 560.50p +5.36%Travis Perkins (TPK) 669.50p +4.86%FTSE 250 - FallersCOLT Telecom Group S.A. (COLT) 118.75p -4.81%Northumbrian Water Group (NWG) 242.25p -4.53%DSG International (DSGI) 24.25p -3.96%Daily Mail and General Trust (DMGT) 300.00p -3.46%SSL International (SSL) 549.50p -3.43%Daejan Holdings (DJAN) 2,100.00p -3.31%Henderson Group (HGG) 97.50p -3.23%Derwent London (DLN) 933.00p -3.17%Brit Insurance Holding (BRE) 197.00p -2.72%Drax Group (DRX) 401.75p -2.55%