I didn't do Phys Systems or Diagnostics (I'm going to be doing that this year), but I can give you some advice for Epi and Immuno.
For Epi, don't worry about not going lectures as most of them are common sense, however make sure that you understand what causes some of the infectious diseases and the pathogenesis covered. For pracs, also don't worry if you don't understand what's going or you sometimes "feel behind". The only thing you need to know at the end of the day is what agars grow what and their appearance as this is what the prac exam will assess you on. Make sure you pay attention during outbreak 1 of your pracs as you will have to write a report about that. Every prac after that you can just chill. For the final exam, rote learn all the diseases, causes, pathogenesis, treatment, etc. as there's always questions about that. There is more advice I can give if you specifically ask me what you need help with but this is generally what you need to know.
For Immuno, you will find it hard to correlate what you learn in pracs and what you learn in lectures. Just make sure that you fill everything out in your prac manual as you will be assessed on the correctness of your manual. I didn't go to lectures as well for this subject because I dozed off in the first half an hour of the first lecture and decided not to go to lectures anymore. You will have an open book flow cytometry test which is really easy if you take notes during the lecture about that topic. There will also be an open prac exam which you should take notes from your previous pracs and write as much as you can in your manual. For the final exam, know the specific receptors on cell and they should pretty much be free marks once you see them. Again, if you come across any other thing you need help with, just ask.