British Land and private equity giant Blackstone have confirmed plans for a major revamp of Broadgate, the huge office complex in the heart of the City of London, which will see new offices built for Swiss bank UBS.In today's statement, British land and Blackstone's joint venture BlueButton said it has entered into exclusive non-binding heads of terms to construct UBS a new building on the site of 4 and 6 Broadgate, a deal which will retain the bank as an anchor tenant in the project.UBS currently rents 850,000 sqft of office space in six of Broadgate's buildings for about £39m a year. The Swiss lender today announced it swung to a better-than-expected first-quarter net profit of 2.2 billion Swiss francs compared with a loss of 1.98 billion francs last year. Pre-tax profit from continuing operations came to 2.81 billion francs, with all business divisions reporting a pre-tax profit.