Waitrose Night Replenishment Assistant interview questions

I applied online and did the standard tests. About a week later I got an email inviting me to an interview. There were about twelve of us there and we had to fill in some forms and hand in our ID to be photocopied. A woman came into the room and told us what we would expect from the day -- it would be a group interview, followed by a one-to-one interview. We were then divided into two groups and taken into a different room where we were given a sheet of laminated paper each, with questions on it. We had to work together as a group and answer these questions as three manager-types observed, which was sort of intimidating. The other interviewees were lovely, but a couple of them dominated the conversation and it was hard to get a word in. Anyway, that took about 30 minutes. We were then each called for a one-to-one interview. This lasted about 15 minutes. The interviewer asked me a few competency based questions and then said I would know my fate within 15 days. I got an email three days later saying I had been unsuccessful. I think I was unsuccessful due to the fact that I was a little bit quiet during the group interview, and I ended up interrupting people a couple of times (the observers might have thought I was being rude?). During the one-to-one, the woman who interviewed me came across as abrupt and unfriendly so I felt quite intimidated. I tried to answer the questions as best as I could and use my previous experiences as reference, as I have worked night shift supermarket roles before -- but I just think nerves got the better of me this time around...