These posts are all really helpful. I have a sales advisor group interview with Mothercare tomorrow evening, and after reading all your posts I'm actually looking forward to it. I'm naturally a confident and enthusiastic person, so the group situation doesn't intimidate me, as I imagine it may do for some others, but I know its important to make myself stand out in a positive way.
If -like me- you don't have children of your own or extensive experience of caring for children, you should probably attempt to prove your knowledge of the products and customers more. Otherwise, I think internet research like this is a great way to boost your confidence.