No.
To start with this is the responsibility of the airline you have purchased a ticket from (i.e. Qantas) to make re-routing/rebooking/other arrangements. Operating carrier cannot be held responsible for a booking with another airline.
Secondly, if this is a full fare ticket (what is your booking class, is it Y? What does T&C say on your booking?) airline is not supposed to impose any sort of penalty for changing/cancelling your flight even after it has departed (it is called fully flexible for a reason).
Thirdly, there's an EC directive which applies to each and every flight departing from the EU which says that in case of cancellation you are entitled to a full refund with no penalties.
Have you put down the name of the operator who told you all these stories? I would strongly recommend sending a note to Qantas explaining your situation and asking to better train their employees.

UPD:I have just checked Qantas own website and, yes, they are supposed to give you a full refund for your flight irrespective of your fare type. Please refer them to section III article 90D (2) of Qantas International Passenger Rules and Fares Tariff.