You've never heard of Cadbury's (who make Dairy Milk)? They're like the biggest chocolate buisness in the Uk. The tour of the factory is great too. Dairy Milks are like milk chocolate bars. But you can get different variations such as bubbly, biscuit, wafer, turkish delight....
Double deckers are sort of like Mars Bars except there are crunchy bits with the caramel top.