Investec has reiterated its 'buy' ratings for all five major UK banks, saying that while the first-half results season will be 'unexciting', lenders are unlikely to provide a negative surprise."With limited scope for negative surprise on impairments and with a predictable weak outlook for revenues, expect a broadly underwhelming picture," said analyst Ian Gordon.The broker labels Barclays (target price of 240p) as a "key value play" and its top pick in the sector. With the stock having outperformed its peers through July in the aftermath of the LIBOR scandal-related sell-off, Investec says that consensus forecasts have edged down. The stock now is extremely cheap, says the broker, and "we believe that starting to refocus the debate onto fundamentals can only assist in supporting the absolute share price performance as well as maintaining its relative outperformance as the focus of the LIBOR debate broadens to other implicated banks and/or regulatory collusion."Standard Chartered (1,800p target price) remains the broker's choice of the 'UK Asians' and is the only bank expected to report a (small) beat against consensus estimates.As for the others, Gordon said: "Lloyds (40p target price) is our preferred restructuring play while RBS (300p target price) appears increasingly speculative. HSBC (600p target price) offers relatively limited upside, and is our 'least preferred' UK bank notwithstanding recent weakness related to its anti-money laundering procedures."The banks were trading broadly flat on Tuesday morning.BC