The UK Secretary of Communities and Local Government has released a draft national participatory budgeting strategy, and is now seeking feedback on the plan.
See http://www.communities.gov.uk/publications/communities/participatorybudgeting

The plan adopts a fairly strong definition of participatory budgeting: "Participatory budgeting engages people in taking decisions on the spending priorities for a defined public budget in their local area. This means engaging residents and community groups to discuss spending priorities, make spending proposals, and vote on them, as well giving local people a role in the scrutiny and monitoring of the process."

The strategy also includes a few case studies and models of PB, and
proposals for launching pilot programs, with the goal of having PB used
in every local authority by 2012.