(ShareCast News) - London's mid-cap index lowered after oil prices dragged mining and oil stocks down.The FTSE 250 index fell 0.19% at 17,644.65 by 1549 BST on Monday.Shares in trading platforms company Fidessa plunged after the company reported a 1.5% decline in year on year pre-tax profit to £19.4m.Analysts at Numis downgraded their rating for Fidessa to 'hold' from 'buy' following the result, and said the outlook was more troublesome than expected.Brent oil fell to a six month low of $50.83 a barrel, dragging down metal prices and subsequently mining and oil companies on the index. Kaz Minerals, which last week lowered its annual targets for by-product gold, fell by 6.11% to 152p, making it the second biggest faller on the index.Similarly Premier Oil and Lonmin fell by 5.75% and 5.7% respectively.OneSavings Bank led the risers, up 4.4% to 303.80p after the company signed a deal for a single platform which enabled lenders to distribute work to and receive work from qualified surveyors.Rising 2.54% to 250.20p, Foxtons Group rose off the back of several analysts' reports which were broadly positive toward the real estate firm. The stock has an average rating of 'hold', and the average 12 month price objective from brokers who have issued ratings is 224.20p.FTSE 250 - RisersOneSavings Bank (OSB) 303.80p +4.40%Foxtons Group (FOXT) 250.20p +2.54%AO World (AO.) 127.00p +2.01%Virgin Money Holdings (UK) (VM.) 433.10p +1.91%Synergy Health (SYR) 1,773.00p +1.90%Poundland Group (PLND) 343.40p +1.84%Hiscox Limited (DI) (HSX) 939.50p +1.51%Riverstone Energy Limited (RSE) 951.00p +1.49%Man Group (EMG) 165.30p +1.47%JD Sports Fashion (JD.) 816.50p +1.43% FTSE 250 - FallersFidessa Group (FDSA) 2,095.00p -12.71%Kaz Minerals (KAZ) 152.00p -6.11%Premier Oil (PMO) 126.20p -5.75%Lonmin (LMI) 49.18p -5.70%Polymetal International (POLY) 432.20p -4.59%Vedanta Resources (VED) 381.40p -4.48%Hunting (HTG) 493.30p -3.93%Acacia Mining (ACA) 230.80p -3.87%Aldermore Group (ALD) 255.30p -3.30%Home Retail Group (HOME) 158.40p -3.00%