Many candy shops in Canada don't sell M&M's, and for me Smarties were a viable alternative. I spent a month in Alberta many years ago, and whenever I had a craving for M&M's, I'd buy a box of Smarties. They must've changed the flavor of the orange colored Smarties to orange in recent years, because I recall many years ago, they were all chocolate flavored. The coffee crisp bars are really good. There is a wafer that "floats" inside, on top of a bubbly coffee cream made from coffee beans, which is all wrapped in a layer of chocolate on the outside. So when you bite into it, you see this wafer (like the Kit Kat wafer) surrounded by little bubbles of air. It sort of has a taste of coffee with cream in it. I've never tried the Mint Aero's.
My all time favorite candy bar is the Snicker bar. Could never find it in Canada, and a Canadian friend of mine said to just look for the Marathon bar. Same thing. LOL!!
My sister-in-law has family in England, and whenever they go visit, they always bring back a ton of chocolates and digestive buisquits. I like the dark chocolate Aeros.
I live in the Pittsburgh area, and our local Giant Eagle supermarket carries many of the Heinz products that are made specifically for the UK, including salad cream, marmalite and baked beans.