Tullow Oil has refinanced its 500m dollar corporate revolving credit facility to boost its balance sheet. The oil and gas company has increased the facility to 750m dollars and extended the tenor to April 2017.Irish building materials group CRH was also making gains today following news that its two European rivals Lafarge and Holcim are to merge, creating a cement-making company with combined annual sales of €32bn. Defensive stocks SSE and Centrica were both on the rise as the wider index fell nearly 1% in mid-afternoon trading. Meanwhile, housebuilders Barratt Developments and Persimmon were both trading in the red after a report by HomeOwners' Alliance raised concerns with the rapid rise in house prices across the UK. The group said that more people now think house prices are a "very serious issue". MPs have demanded further explanations from Business Secretary Vince Cable after the National Audit Office (NAO) criticised the over-cautious approach of the government's privatisation of the Royal Mail, pushing the stock firmly lower. Cable has been recalled by the House of Commons Business Committee on April 29th to answer claims that he mis-priced the sale and allowed City traders to make considerable instant profits at the expense of taxpayers.British department store chain Marks & Spencer (M&S) was also in the red ahead of what is expected to underwhelm with its latest trading update on Thursday. The FTSE 100 company is widely expected to post a decline of 1% in its clothing division in the first three months of the year, while sales within the Food division are forecast to be flat. FTSE 100 - RisersCentrica (CNA) 335.20p +2.04%SSE (SSE) 1,485.00p +0.68%Tullow Oil (TLW) 803.50p +0.44%Morrison (Wm) Supermarkets (MRW) 205.60p +0.39%Rexam (REX) 503.50p +0.30%CRH (CRH) 1,778.00p +0.17%Royal Dutch Shell 'A' (RDSA) 2,218.00p +0.09%Babcock International Group (BAB) 1,415.00p +0.07%Bunzl (BNZL) 1,620.00p +0.06%Unilever (ULVR) 2,539.00p +0.04%FTSE 100 - FallersBarratt Developments (BDEV) 394.90p -3.66%Mondi (MNDI) 1,051.00p -2.95%Hargreaves Lansdown (HL.) 1,395.00p -2.86%Royal Mail (RMG) 534.50p -2.73%GKN (GKN) 395.10p -2.71%St James's Place (STJ) 824.50p -2.37%ARM Holdings (ARM) 972.50p -2.36%Lloyds Banking Group (LLOY) 75.73p -2.23%Persimmon (PSN) 1,317.00p -2.15%International Consolidated Airlines Group SA (CDI) (IAG) 434.50p -1.90%NR