Originally Posted by
Mwenenzi
As above if you have not taken the first flight cancel (with full refund) or ask QF to rebook when PE seat is available. Asking for compensation may result in a less desirable outcome for you. QF may be less co-operative with your situation
The fares paid seem fairly low (although I am not familiar with ex-PER pricing) so cancelling and booking an alternative flight may well cost the OP more in ticket cost for the new flight.
I would be inclined to ask to be rebooked on another day if I do not want to travel Y. Asking for compensation at the same time will probably result in less cooperation from QF as you say.