Awesome well done man! I hear Manchester's interviews are...interesting.
They're not so bad, I'd say less daunting than the traditional 30 minute job interview style grilling session.
You basically do a mock PBL discussion with about 8 other applicants to see how comfortable you are with the format. You'll get given a medical ethics issue to debate so they can assess how you do in a group. Nothing too intense as they're not looking for prior medical knowledge or anything.
After that you'll have three 5-minute interviews. One will be asking you to reflect on your experience of PBL, the other two will be on different parts of your UCAS application. They're very quick so you don't go into too much depth.