The FTSE 100 Index is down 6.1 at 5130.2 at mid-morning, having lost earlier gains.
Weaker banking stocks are overshadowing the warm reception given to Vodafone's results.
Barclays is off 3% or 20p to 600p after warning of higher costs and bad debt provisions in a statement ahead of its interim results in August.
Royal Bank of Scotland is down 23p to £19.80 (€31.22); Lloyds TSB has fallen 10p to 740p; and Standard Chartered has eased 3p to 815p.
The City has welcomed Vodafone's results, despite huge bottom-line losses, sending its share price up 4p at 109p as investors focused on its underlying performance, which showed strong profits growth ahead of one-off costs
Rival mmO2 has edged up 1p to 49½p.
Among the tech stocks, computer services firm Logica is up 3¾p at 229p; and software firm Sage has climbed 1½p higher to 162p.
Food retailers are weaker, with Sainsbury's down 5¾p at 365p ahead of its annual results tomorrow; Safeway down 6p to 299p; Morrisons easing by 6p to 220p; and Tesco falling back 2¾p to 246¾p. Marks & Spencer is down 5½p to 386p.
Durex condoms to Scholl footwear group SSL International is down 4% or 16p to 375p after reporting sharply lower full-year following action to solve problems with excess stocks.
But Hull-based Kingston Communications is up 1% or 1¼p to 90½p after saying it had enjoyed a 'solid' performance in the last year and was well placed to maintain growth.