Initial online tests, standard numerical reasoning etc, followed by a 1:1 phone interview, which consisted of competency based questions and why I was applying to the company. Finally an assessment centre (6 hours) which involved a pre-prepared case (20 minute presentation), group work (solving a case), and an interview (further competency based questions, knowledge of the company, why I'm applying, and on the spot business questions).
Negative experience due to: Long delays between stages (3 months between first applying and the assessment centre), yet only 1 weeks notice before the assessment centre date, communication disorganisation and very small travel reimbursement (maximum £75) regardless of how far you've had to travel. Overall, made the company look complacent about their selection process and (I believe) put off good quality candidates.