The assessment process is not the most difficult assessment. The maths is very basic, it is literarily the basic GCSE maths very easy. The aptitude test is not bad but if you are IT inclined you will fly through it. As for the set notation and Venn diagram you MUST revise if you want to do well, don't underestimate it. The 3X 5mins interview is what I absolutely don't understand what exactly there are looking for. They should be more transparent in terms of an overall pass mark and give you feedback, not a generic feedback.