I filled out the brief online application form, took two multiple-choice situational judgement tests, then completed the lengthier questions. A week later I received a call letting me know that I was being invited to the store for an interview, which took place a few days later. I thought I may have to do a group interview, but it was just a 1-to-1 one. I can't remember exactly what I was asked, but it was something like "tell me about yourself", "tell me about a time when you either gave, or were given, feedback on something", "have you ever had to question a manager's authority?" and "why do you want to work for Waitrose?". There were then a couple of questions about how I would ensure the quality of stock and what a customer may want to know about a product. I was then given 20 minutes to read through 3 sheets of fictional in-store scenarios, pick out the three most serious/problematic ones, and then write a brief 'report' on why I chose the examples and what action plan I'd implement to solve the problems (easier than it sounds).
I was told that someone would call me the following day to let me know if I had been successful, but no one called. Fortunately, I did get a call four days later and was offered the job, and a week later I received an email with the offer, which I accepted.