I've tried to take a picutre, but you can't really see it clearly. Here they are, anyway:
In this on you can see the indentations pretty well. Below, the sort of white blob in the middle is the one that is really painful. It is a mark like the rest of them, it just looks like a blob here!
Needless to say, I will be wearing some gauze over the brackets tonight. I find a piece of gauze more effective to just cover the whole lot, and it doesn't matter since no-one will see me with it in! lol.
I wonder if it rubs because I'm a mouth-breather, so have a very dry mouth in which a bracket can stick to my lip in. Probably!