(ShareCast News) - The FTSE 250 crawled back into positive territory on Monday afternoon after the UK mid-cap lost momentum from its early spike.By 1550 BST the index was up 0.12% at 16,913.29, helped along by the steady climbing of Pace despite the set-top box maker's £1.4bn proposed merger with US-based Arris being hit by regulatory delays. With antitrust watchdogs in Brazil, Colombia and the US all wanting to examine the deal further, Arris announced that it now believed that closing of the transaction will not occur until late December or the first quarter of 2016.Rising even higher was NMC Health, retracing some of its aggressive move south on Friday. The company still harbours aspirations of acquiring fellow Abu Dhabi health group Al Noor, even though the target firm has agreed a reverse takeover with larger South African rival Mediclinic. NMC last week reiterated its belief in the competitiveness of its possible offer but admitted it had been denied much meaningful engagement with the board of Al Noor.Oil companies made up many of the fallers on Monday, as various factors weighed on the sector, seeing stocks such as Nostrum Oil & Gas, Premier Oil and Tullow slipping lower.News of China's economic growth slowing below 7% for the first time since the financial crisis cast a cloud over the demand for natural resources.Ratings agency Moody's also trimmed its forecasts for oil prices, estimating that both decelerating demand and oversupply issues will make any rebound slower than expected. The rating agency downgraded it 2016 price assumptions for Brent crude to $53 per barrel, down from $57, with WTI given a haircut to $48 per barrel from $52.Poor quarterly results from Halliburton, a few days after dismal numbers from fellow oil field giant Schlumberger, also had read across for UK-listed companies. Energy services provider Hunting and global oilfield services company Petrofac were both sent lower as their US peers lamented weak demand for services to the energy industry.Market MoversFTSE 100 (UKX) 6,346.70 -0.49%FTSE 250 (MCX) 16,915.91 0.14%FTSE 250 - RisersNMC Health (NMC) 776.50p 6.22%Pace (PIC) 382.70p 3.63%Big Yellow Group (BYG) 709.50p 3.35%esure Group (ESUR) 249.50p 3.10%Provident Financial (PFG) 3,449.00p 2.96%Ted Baker (TED) 2,859.00p 2.84%Workspace Group (WKP) 934.00p 2.64%Booker Group (BOK) 182.00p 2.48%OneSavings Bank (OSB) 375.80p 2.45%Wetherspoon (J.D.) (JDW) 758.50p 2.43%FTSE 250 - FallersNostrum Oil & Gas (NOG) 472.60p -9.46%Premier Oil (PMO) 80.20p -6.74%Kaz Minerals (KAZ) 128.10p -6.29%Evraz (EVR) 88.05p -5.32%Tullow Oil (TLW) 230.80p -5.22%Vedanta Resources (VED) 549.00p -4.77%Ophir Energy (OPHR) 93.55p -4.54%Hunting (HTG) 411.00p -4.44%Petrofac Ltd. (PFC) 899.50p -3.69%AO World (AO.) 151.10p -3.27%