I get the impression that if an organisation has a suitable project then they only need to ask the Probation Service (or whoever) to get a team in to help out. Mind you, there's a raft of Health & Safety legislation that would probably get in the way of doing jobs that might be even mildly difficult, then there's the Human Rights Act to consider...!!!
Sid: Have a word with Ant at the Mill (01304 823292) about contacting the Community Payback people. There's usually one of their supervisors on site too so it might be worth popping into the Mill and having a chat him.