Well Done on getting a store interview! What happened at my interview was we were taken into a room (there was about 6 of us) and were paired up. We had to find out 3 fun facts about our partner and then introduce them to the rest of the group. After that, there was a mini questionnaire thing that gave us 3 different scenarios. We just had to say what we would do. Then, there was a clothes rack on one side of the room. We were told to pick an item and were given about 5-10 minutes to plan out what we were going to say. We then had to sell the item to the interview people. We were then given a 5-10 minute break. After that, we were called for 1-1 interviews. They are pretty much exactly the same the phone interview.
It sounds a lot scarier than it is! It's really relaxed and chatty. You'll be fine, I'm sure! Good luck for next week!