HP20:
My best tip for any interview when you'll be asked about 'competencies' - look up competency based interviews on google - think about your past experiences and what you've learned, struggled with, achieved, succeeded, etc and the skills associated with those experiences. If you have gaps in your CV or work experience, make sure you are comfortable explaining the reasons why. Be confident speaking about the choices you've made in your life and the reasons behind those too.
The real thing I see people struggle with in interviews is recalling an appropriate example for a skill - I'm usually pretty sure they have the skills, but thinking of something immediately can be difficult if you haven't prepared. I generally recommend the book 'Brilliant Answers to Tough Interview Questions' as it's good at explaining how to tackle questions and structure your answers, but that might be a bit late for you now!
Good luck!