1st stage - Send application along with some answers to some questions (biggest achievement, what do you know about Skyscanner, etc.)
2nd stage - fill out personality test (very short)
3rd stage - Competency-based telephone interview
4th stage - Assessment centre. Group exercise + presentation - in my case we had to present fictional new products that Skyscanner were interested in. This was followed by a networking lunch with the managers. Finally there was a technical interview - I was presented with two fictional case studies, and was asked various marketing and commercial questions.
Received a telephone call about 10 days later.