First they screen your application and then send a non technical test to do after which, if successful, you get invited to do a hireVue platform video interview. There were 5 questions i believe competency and situation based. Then they replied really fast the next day inviting me to their assessment day in December. The assessment day itself is very relaxed and just the right amount of challenging. I wouldn't worry too much just prepare normal interview questions like why Vodafone. The day itself was split in three sections, one was 1-1 Presentation where you are given a case study and have about 20 mins to prep and then deliver ur points for 10 mins and a further 10 mins for questions/answers. The next activity was a 1-1 interview which was based around me and how I would approach certain scenarios. Don't stress too much and just be yourself in the interview, they just want to know how you would behave and fit in the company. Lastly in the group exercise, make sure you don't talk over people but don't be quiet and reserved. Make sure you get your points across without talking over. Overall, the day was very well organised and we had plenty of breaks in-between. Definitely, the nicest assessment I have been to.

One sided interview, questions about how you would act in certain scenarios along with business logic and general logical thinking/reading comprehension. Nothing relating to specific technical roles so I recommend looking into how these processes normally ask questions.