UK stocks slipped in early trading on Friday, giving up some gains made yesterday on the back of the post-Fed rally, as focus again returns to Greece with talks over the debt swap continuing to weigh on investors' minds.Both sides taking part in the negotiations over the degree of private sector involvement (PSI) in Greece see progress in the talks, according to Reuters. The main bone of contention is whether and to what degree European Union (EU) public sector entities, such as national governments and the European Central Bank (ECB), participate in any agreement. The 'hair cut' which will be applied to private sector debt holders is seen depending on the answer to that question. The EU's economic affairs commissioner, Olli Rehn, is being cited by Reuters as having said that, "there is likely to be some increased need of official sector funding, but not anything dramatic." However, Sources at the ECB are reported to have said that the central bank is no closer to reaching such a conclusion following a meeting late last night. BP FALLS AS MACONDO ISSUES DRAG ONIntegrated oil giant BP has again called on US oil services company Transocean to put its hand in its pocket to pay its share of the clean-up costs for the Macondo oil spill after a US court ruling on Thursday relating to the Deepwater Horizon tragedy.The ruling makes clear that contractors will be held accountable for their actions under the law, a BP statement said. BP was among the worst performers on the FTSE 100 in the opening minutes.Public sector services group Serco also fell despite having signed a contract with the UK Ministry of Defence (MoD) to provide training and support to the British Army prior to deployment on operations around the world. The contract has a total value to Serco of £55m through to December 2014.On the FTSE 250, gold miner African Barrick Gold led the riser after hiking its previous resource estimate fourfold for the Tusker deposit at the Nyanzaga Project in Tanzania.London Stock Exchange rose after reporting that total income in the third quarter was up 17% year-on-year. However, the bourses operator added that the fourth quarter has started with subdued secondary market trading.Healthcare outsourcing group Synergy fell after saying that while trading has been in line with expectations, it will incur a £2.3m one-off charge after a "re-organisation" in response to macroeconomic risks.Aveva, the Cambridge based engineering technology company, fell despite releasing a bullish management statement. The company attempted to put to rest any qualms that it might be suffering similar problems in China to its rival, Invensys.Also underwhelming investors was plastic packaging firm RPS after saying that revenues in the quarter ended December 31st were significantly ahead of last year.BCFTSE 100 - RisersMan Group (EMG) 119.60p +1.10%BAE Systems (BA.) 316.70p +0.60%Essar Energy (ESSR) 136.50p +0.59%Imperial Tobacco Group (IMT) 2,266.00p +0.58%Rolls-Royce Holdings (RR.) 755.00p +0.47%Polymetal International (POLY) 1,157.00p +0.43%Tesco (TSCO) 324.20p +0.37%Tullow Oil (TLW) 1,395.00p +0.36%Pearson (PSON) 1,181.00p +0.34%Severn Trent (SVT) 1,552.00p +0.32%FTSE 100 - FallersInterContinental Hotels Group (IHG) 1,328.00p -2.14%Sage Group (SGE) 296.00p -1.73%Evraz (EVR) 450.30p -1.55%BP (BP.) 471.10p -1.19%BT Group (BT.A) 205.50p -1.11%ARM Holdings (ARM) 591.50p -1.09%Wolseley (WOS) 2,250.00p -1.06%Rio Tinto (RIO) 3,852.50p -1.04%Barclays (BARC) 220.55p -1.03%Anglo American (AAL) 2,709.50p -1.00%FTSE 250 - RisersAfrican Barrick Gold (ABG) 508.00p +3.78%Brown (N.) Group (BWNG) 238.00p +2.85%Regus (RGU) 100.60p +1.62%JD Wetherspoon (JDW) 419.20p +1.62%London Stock Exchange Group (LSE) 893.00p +1.30%PayPoint (PAY) 565.50p +1.25%Kier Group (KIE) 1,376.00p +1.18%Gem Diamonds Ltd. (DI) (GEMD) 218.00p +1.07%easyJet (EZJ) 449.90p +0.99%Halfords Group (HFD) 318.50p +0.95%FTSE 250 - FallersPhoenix Group Holdings (DI) (PHNX) 550.50p -4.26%Morgan Crucible Co (MGCR) 297.90p -4.12%F&C Asset Management (FCAM) 65.20p -2.47%PZ Cussons (PZC) 296.40p -2.21%Carpetright (CPR) 594.00p -2.14%Cobham (COB) 185.10p -2.12%Rightmove (RMV) 1,279.00p -1.99%Greggs (GRG) 501.50p -1.67%Afren (AFR) 126.50p -1.63%Domino's Pizza UK & IRL (DOM) 464.20p -1.63%