Farmfoods may conduct group interviews, as a lot of superstores do. I think it depends on how many people are applying for the job, as they may not have time to interview everybody separately straight away and so group interviews give them a chance to narrow it down a bit more easily.
If there is a group interview, you will probably be asked to do some activity so the interviewer(s) can see how well you work with others. They will be looking to see if you’re more of a team leader or a team worker. Your skills with other people are also very important in a store like Farmfoods, where you are working with other people all the time and also dealing with customers on a day-to-day basis.