An upgrade from Liberum Capital helped lift shares in Lonmin on Monday. The broker now recommends investors keep 'hold' of the mining stock.BBA Aviation also took off after announcing that its Signature Flight Support business has agreed to acquire the fixed-base operator assets of Wiggins Airways at Manchester-Boston Regional Airport from US cargo airline Ameriflight for $16.2m. The acquisition is expected to be earnings enhancing in the first full year of ownership and meet BBA Aviation's targets for returns by year three.Meanwhile, Evraz was lower after JP Morgan Cazenove cut its rating on the stock from 'neutral' to 'underweight'.Close Brothers dropped after the news it has sold its German securities business, Close Brothers Seydler Bank. The sale was made for a cash consideration of £36m, with proceeds to be reinvested in the merchant banking group's core businesses of lending, wealth management and securities trading in the UK.Oil stocks also pressured the market lower as crude prices retreated. Premier Oil, Cairn Energy and Ophir were all in the red.FTSE 250 - RisersFerrexpo (FXPO) 91.40p +5.73%Lonmin (LMI) 187.50p +3.31%Go-Ahead Group (GOG) 2,430.00p +3.23%Bwin.party Digital Entertainment (BPTY) 91.00p +2.82%Telecity Group (TCY) 700.00p +2.12%LondonMetric Property (LMP) 138.40p +1.91%Bovis Homes Group (BVS) 809.00p +1.89%Howden Joinery Group (HWDN) 330.50p +1.82%Afren (AFR) 99.25p +1.79%Barratt Developments (BDEV) 403.20p +1.72%FTSE 250 - FallersJust Eat (JE.) 264.90p -3.88%Evraz (EVR) 124.00p -3.65%Debenhams (DEB) 58.10p -3.57%Victrex plc (VCT) 1,550.00p -3.25%Premier Oil (PMO) 252.60p -3.14%Cairn Energy (CNE) 157.90p -3.13%NMC Health (NMC) 476.40p -2.78%Ophir Energy (OPHR) 189.00p -2.78%SIG (SHI) 151.20p -2.77%Supergroup (SGP) 1,035.00p -2.63%