So contrary to the other interview stories here, I had a group one (but I'll put this down to the fact that I applied for the Christmas temporary position).
The person 'interviewing' us said she'd be taking notes based on observations on the way we interacted as a group. So we did some group exercises, and the first was to find out as much as we could as our partners. The guy I was with didn't cooperate with me much but I tried my best. After that, we fedback this information to the group.
Next exercise, we were put into groups of fours to create a superhero that best describes Argos, and is the perfect representation of an employee. Again, we did a small presentation of that and were judged on our personalities and the way we worked as a team.
Then we were told to show someone our right to work documents, write down when we were available to do shifts etc. Lastly, we had a brief q&a session and that was it. We find out on Tuesday when we're successful. We don't know about pay until we're actually given the job offer.