My advice would be, identify all skills that you'll be tested on - from the candidate handbook.
Then practice each one, videoing yourself as you go.
Mark your performance in accordance with Royal Marsden standard, including the interpersonal skills that you use.
When you feel that your anxiety when performing these skills (in a non- realistic set-up) is diminished, ask someone to observe you and assess - again using Marsden. Ask them for and be open to feedback