There are general labelling rules for milk and milk products (for example, labelling milk as an allergen). Drinking milk is covered by The Drinking Milk England Regulations 2008
The Spreadable Fats (Marketing Standards) and the Milk and Milk Products (Protection of Designations) (England) Regulations 2008 require milk and milk products intended for human consumption to comply with certain specifications for names and composition.
For condensed milk and dried milk, there are specific compositional and labelling requirements in The Condensed and Dried Milk (England) Regulations 2015 (for example, fat and milk solid content).
The Caseins and Caseinates (England) Regulations 2017 contain specific compositional and labelling requirements for caseins and caseinates (for example, milk protein content).