@AjasLipstick: I'm English but live in Australia and here, the big shops have a policy where they "can" ask to see inside your bag as you leave
The bag has to be larger than a sheet of A4 paper, and needs to have a sample size shown in store (or used to, I know size is accurate). They can't touch anything in your bag, but can ask you to move an obstructing item. You can refuse to allow them to look, and they, in turn, can ask you to leave store.
That being said, I have only once, in decades of shopping, been asked to check my bag at a supermarket and that was because I did look suspicious - really scruffy, late at night, in a tearing hurry to get to the other local supermarket before it closed as I wanted something specific for work the next day and the one I was in didn't have it.
I gather K-Mart checks a lot, and I recently bought something at JB HiFi and they checked, and that was another nail in their coffin. I will never go there again as they must be the most awful place on the face of the earth - cluttered, disorganised, hopeless service and not even very cheap.
Actually, thinking about it, he probably shouldn't have checked my purchase as it was an ereader and in a bag which was smaller than a sheet of A4.
However, that's a long way of saying that I have virtually never had a bag check in Australia.