Easyjet assessment day is much more relaxed and easy going than other airlines I had applied for. My number one advise is to be yourself and smile, include everyone and socialise. Think of answers to questions for the interview before you go, you will feel more gathered this way with examples in mind. The assessment day consists of 3 group tasks then lunch if you make the afternoon you'll get an interview 2-1 and the interviewers make you feel really relaxed and explain everything to you before starting. I was finished in 15 mins when it was meant to take 30. It's not about talking for ages rambling on, it's better to say less with lots of information stay on the question they're asking you and don't change it to what you want it to be. If you don't perform to a high enough level you will be sent home. Don't give up! Good luck :)