The most recent year for which public expenditure on consultancy is available 2008-09. These data were published by the Office of Government Commerce alongside Budget 2010 in the “Public Sector Procurement Expenditure Survey 2009”
http://www.ogc.gov.uk/publicspending
The expenditure set out here will be reduced by 50 per cent. a year by 2012-13, as set in the pre-Budget report 2009.