tbh id just have a browse, i ended up in a large tesco near me on nights, since I dont really have commitments in a gap year, all the overtime i could ask for, and nights pay really well for an entry level job. Jobs are abundant too around Christmas for temps, and if the store is large enough and you can work they tend to keep you on. But id browse consistently until they come around as a backup, the sooner you start, the more you can save.