The Australian National University is arguably the best university in Australia, but the examiners mark very harshly.
Bear in mind that at the end of your 3-year PPE degree at the ANU, you will only graduate with an ordinary degree. Investment banking is competitive and so it may look good for you if you have an honours degree. However, unlike in the UK, getting into the honours program (a special 4th year, in which you write a thesis, after the initial 3-year degree) in Australia is usually very competitive. Honours is reserved for top students. Typically, only fewer than 10 students (not ≥10% as is the case in the UK!) graduate with first class honours in each cohort at the ANU. This is why 3-year Australian degrees are arguably less portable if you want to work elsewhere in the world due to the tendency of employers to equate UK honours with Australian honours.
In stark contrast, completing a 3-year degree in the UK will give you an honours degree unless you're thick. 10% or more of the cohort will graduate with firsts. Your degree will be recognised back home in India as an honours degree. However (as rightly pointed out by Snufkin), the downside is that it would be harder to migrate to the UK with the current Brexit situation, and I understand that you would want to settle in either the UK or Australia.
It's your choice, but my advice would be either to go all the way in Australia (4-year honours degree in the ANU, aiming to be one of the top 10 students with firsts) or to get a first in the UK (top ≥10% of your year).