Keller Group was a top riser after reporting better-than-expected first-half results. Pre-tax profit before exceptional items increased by 21% year-on-year to £32.5m in the six months to 30 June. Liberum gave the engineering group a 'buy' rating after the results, saying it sees "compelling attractions". Home Retail Group gained after a report from Markit showed UK housing construction activity in July registered the sharpest rise since November 2003, led by a record pace of job creation and a shortage of supplies.Telecity Group slumped after Investec warned that foreign exchange movements might constrain short-term performance. The company, however, reported profits before tax grew 13.6% to reach £49.97m during the six months ended 30 June.Other fallers included PayPoint, Afren and Imagination Technologies.FTSE 250 - RisersKeller Group (KLR) 908.00p +3.77%NMC Health (NMC) 478.00p +3.69%Home Retail Group (HOME) 168.10p +3.45%Perform Group (PER) 221.30p +2.93%Alent (ALNT) 340.00p +2.91%Man Group (EMG) 119.80p +2.57%Just Retirement Group (JRG) 140.40p +2.41%esure Group (ESUR) 262.20p +1.94%Kazakhmys (KAZ) 321.50p +1.93%Centamin (DI) (CEY) 72.50p +1.90%FTSE 250 - FallersPayPoint (PAY) 1,035.00p -4.78%Telecity Group (TCY) 762.50p -3.60%Afren (AFR) 110.10p -3.51%Imagination Technologies Group (IMG) 182.90p -3.23%Infinis Energy (INFI) 214.90p -3.20%Domino Printing Sciences (DNO) 596.00p -3.09%FirstGroup (FGP) 122.00p -2.71%Hochschild Mining (HOC) 158.40p -2.34%Rank Group (RNK) 158.10p -2.17%Dignity (DTY) 1,359.00p -2.16%RD