So, for this question, I will ask as if my visa has been cancelled prematurely and I have received an obligation de quitter le territoire français (OQTF).
Formally, an OQTF does not ban you from reentering France. In practice, it's a bit moot because many people who do get an OQTF also need a visa to come back and most of them would not be in a position to secure one easily. Which is also why the rules stayed that way for a long time.
Recently, the law added a new separate measure to ban people from reentering France (outside of an “expulsion” or an “arrêt“arrêté de reconduite à la frontière” which have always entailed a ban) called an “interdiction de retour sur le territoire français”. Cimade reveals that about a fourth of OQTF are accompanied by an IRTF.
If I receive a OQTF, I was just wondering if I would be able to re-enter France/the Schengen as a tourist and stay for 90 days visa-free as an Australian ? E.g. if I went to England for 1 night, got my stamps on the way out of France, into London, and back into France?
Theoretically yes but remember that you do not have any unconditional right to enter France (or the UK) and border guards are always entitled to evaluate the purpose of your stay (and whether you fulfilled a bunch of other requirements like having enough money). You would present yourself to the border with no job and a proven willingness to settle abroad i.e. objective facts that make the purpose of your stay and your intent to leave the country after 90 days (or six months for the UK) highly doubtful. In fact, it's not obvious to me you would even make it to London (as opposed to being escorted to a flight to Australia).