Hi there 😊
I'm a current pharmacy student who did an interview for Manchester for pharmacy a few years ago and I checked and the format is still the same so I can help advise you.
So it's an online interview liked you mentioned and there is one interviewer and for me it felt like having a conversation about the university and pharmacy. I think it took around 20 minutes overall.
The best way I would say to prepare is look at the university course structure, why Manchester, why pharmacy, look over the Standards of Pharmacy Professional etc. There are some common questions that are asked so prep some answers for them. There are some great general resources on The Student Room under interview prep. I would say practice your answers but you don't want to over rehearse them so then it sounds like you're reading from a script.
Good luck with your interview and I hoped this helped!
University of Bath