Did an online questionnaire which I passed and was then able to schedule an interview that week. Interview had a roleplay which was pretty simple. You are a customer sales assistant at a fictional company and have to help a customer. You are given a pack of info of the stuff in stock and any offers. There will be an item out of stock and the interviewer will ask for it and then you have to offer a substitute which is given on the info sheet. Make the customer aware of the offers and help them with anything else they want. Then interview with store manager about general stuff regarding yourself. Overall I passed their assessment but they said they chose someone else for that store. Since I passed the assessment however, if I wanted to work at a different M&S, I could skip the roleplay and go straight to the manager interview.

Very laid back, three interview questions (why M&S?, why would you fit the role etc) then asked for right to work and availability. Called back a few days later (after the weekend) to be offered the position.