You can almost certainly change your Aus/dollar TCs but you will almost certainly be charged for doing it. US dollar TCs are FOC... Neil.
On Princess Cruises there is no cash handled for anything onboard. You use you cruise card that charges everything to your onboard account and then gets charged to your credit card. Princess make a charge of I think 3% to convert the account which is in US Dollars back into sterling if you are using a sterling credit card.
This is why you should always insist that they do not convert your account but charge it in dollars. Nationwide and the Post Office credit cards give you an even better rate than the tourist rate. ... Neil.
I have a Thomas Cook Credit Card that also does not charge to convert foreign transactions into Sterling.
However, when on my last Princess Cruise despite completing the necessary paperwork for non conversion by Princess they still converted. It was reconverted back to dollars after I raised merry hell at the pursers desk and fortunately was able to produce a photocopy of the form I had handed in on embarkation, did they have egg on their faces. My tolerance level of ineffeciency by these large corporate organisations is rather low.
I feel their lack of training to some staff, needs attention.