Thought I'd do a pretty in depth account because that's what I personally like to read!
After the online application and questionnaires (which were pretty hefty, longer than a few other similar online quizzes I've done) I was emailed straight away saying I'd been offered an interview, which I needed to choose online. Just so happened the only slot they had was the next day so it was a very quick turn around.
Like most of these reviews say, it started with a role play. It was a bit nerve-wracking - I've had plenty of customer service experience, but I've never had to do a role play in an interview. I'd definitely definitely suggest reading through a few of these entries and working out a basic plan of how you'd react. Basically, you go into a room with the assessor and are given about 6 laminated sheets of paper with info on. They leave the room for 15 mins while you read the info and make as many notes as you want. After the 15 mins was up, the assessor came back into the room and from that moment they take the role of an imaginary customer. My scenario was based on me working in the kids dept and a customer is looking for a swimsuit for their daughter. The one they wanted is naturally out of stock, so you have to act accordingly. Basically: make eye contact; ask if they need any help; ask them any questions about their needs; (the item they want will obv be out of stock, but double check) ask when they need it for; if immediately, offer to phone nearby stores/suggest click & collect; see if they're interested in any similar alternatives; ask if they need any help with something else (at this point, big up the in-store promotion - all is clearly shown on the info cards). the assesor told me I did a really good job and did one of the best she'd seen, which was so nice especially because I'd been nervous!
At this point, the assessor leaves the room to mark you, she came back and told me I'd done really well, gave me some feedback and said that I'd passed. I've read that others had to do a self evaluation sheet, but I didn't. Then she left and said the department manager would be with me soon to have my interview.
In the actual interview part, the questions were basically like any other interview. Make sure you go on the M&S website prior to the day and read up a bit about their ethics. It was quite informal and the manager was so friendly and chatty in between questions. It was more of a conversation really. We then went through the hours and she left the room for a minute, came back and offered me the job on the spot, which was very flattering! I accepted and I have my induction in a few days.