Had one screening phone call with HR and another panel interview with potential supervisors. They said I wouldn't need to prepare for the HR call, but this is not true as they ask you specific questions about the company, the area of the business you'll be working in, and the nature of the role. Make sure you do your reading, especially of their website. The panel interview was formal but friendly. It covered competency based questions, questions about the company, personal questions (e.g. why you want to work there, how do you like to be supervised, what's your presentation style), and a 30 minute task at the end. It took about 2 hours, so quite long, but there's plenty of time for you to ask your own questions.