This introduction to partnership and collaboration by Senscot Legal, published online by Partnership for Procurement (P4P), contains more useful information and commentary on these issues.
Partnership for Procurement has also produced a Collaboration Toolkit aimed at third sector organisations who are considering working together with others to pool resources, deliver new products/services or to do things more innovatively.
Remember, this is a complicated area. The information on this website is necessarily general and in summary form only. There is no substitute for taking legal and tax advice at an early stage.