THE Co-operative Group is buying 21 chemists' shops from Alliance Boots, which has signed contracts for the sale of almost all of the branches it put on the market after its é7bn merger last year. The group agreed to dispose of 96 sites, as part of the approval from competition authorities for the Boots' link-up with Alliance UniChem. Now the Co-op's Middleton-based pharmacy division has agreed to snap up branches in County Durham, Northumberland, East Anglia, Devon and Somerset, to take the number of branches in the group to 454.