Choosing legal structures, registration with companies house, market research, business plans, democratic decision making, legal requirements & responsibilities, finances and a few bits on running the thing once you've set it up.
Download for free here: http://www.green-shopping.co.uk/how-to-set-up-a-workers-co-op.html
If you want to buy this useful booklet as a spiral bound hard copy for £6.00 please go to http://radicalroutes.org.uk/publications-and-resources.html. This copy is laid out one page to an A5 sheet. If you have any questions, please feel free to talk to 'Seeds for Change' Lancaster(www.seedsforchange.org.uk) who prepared the booklet or to the RR Trading Co-ops Network or ask Co-ops UK.