In relation to refurbishment works at Downing street I refer the hon. Member to the answer given to the right hon. Member for Horsham (Mr. Maude) on 25 February 2010, Official Report, column 695W.
Refurbishment work at 70 Whitehall over the past 24 months has focused primarily on accessibility, sustainability and infrastructure improvements (including installing modernised IT and telecommunications infrastructure). The work has also involved upgrading the building fabric (including installation of additional insulation to external walls and roofs). In addition, cellular office space in the less historically sensitive parts of 70 Whitehall has been replaced as part of the refurbishment work to provide modernised open plan space, contributing to increasing capacity and efficiency.