I couldn't tell you the breakdown from scene to scene, but most of the cast were non-actors: it was all part of Loach's push for authenticity. For example; the foodbank scene was shot in a real distribution centre in Newcastle (the Church of the Venerable Bede), and most of the people in that scene were real-life volunteers and "customers".
-- "So I've got bullets, but no gun. That's quite Zen."
Ken Loach likes to cast comedians and musicians as well as relatively unknown actors. Dave Johns was a brickie who became a stand up and acted in a few plays so he was perfect for the role.
The other trick Loach does is to get local non-actors who work in those roles or similar roles and have them 'behave' rather than act. That can be hit and miss and there were a lot of misses.