Some good substitutes for double cream are milk and butter, cottage cheese and milk, Greek yogurt, and skim milk and cornstarch. They are good substitutes because of their low fat content.
Melt 1/3 cup of unsalted butter, and add 3/4 cup milk for recipes that do not call for whipped heavy cream. Add 1 tablespoon flour and mix well when you use low-fat milk.
Use 1 cup of skimmed milk, and add 2 tablespoons cornstarch, then whisk for three to four minutes to make a double cream substitute.
Greek yogurt is thick, so it makes a better substitute for double cream than regular yogurt. Use equal amounts of yogurt and whole milk to retain some taste of fat. Cook on low heat when using Greek yogurt because it has a tendency to curdle when heated too fast.
To make a reduced calorie substitute for heavy cream, combine equal amounts of cottage cheese and no-fat milk powder, and mix well until there are no lumps. Skimmed milk can substitute for powdered milk.