The guidelines in the UK for starting children on full fat cows milk are from 12 months of age. Instead of formula you can pour full fat cows milk into your child's bottle or cup and it can be warmed or given at room temperature. However, babies can have full fat cows milk from 6 months if it is added to breakfast cereal or used for preparing food through the day. The primary reason for not giving cows milk before 12 months is formula and breast milk have the required iron that your child needs up to 12 months. After 12 months your child will get all the iron they need from food.
They don't need to continue with formula after 12 months but you can buy follow on milk for babies 12 months + but this is not necessary.