Not very familiar with the new syllabus, but in the old syllabus the y11 and 12 phys chem content were quite different. E.g. circuits were in y11 and it wasn't examined in y12 (I remember skipping that topic y11). If that's still the case, then you could technically just skip it.
The main areas from year 11 physics that you will use in year 12 are the electromagnetism topic (but no circuits in year 12), gravitational field stuff but overall not really that much so best to just start year 12 content