ModelFlyer. Have a look at my post
here on the Cryanair thread. [oops - edited to correct this.] Schedule changes are not currently regulated by the EC under Regulation 261/2004, but they are thinking about it. But hurry, the consultation closes 1 March. (Edited to add. Note that FR was refusing to give a full refund despite what it says in their terms and conditions.)
I'd also ask the
AUC how they view the airline's policy. I suspect they would be prepared to suggest that the full amount should be refunded for a 'schedule change' of 4 days.
Even though a regulation doesn't exist the contract still has to comply with contract law. I'm not a lawyer but I'm fairly certain that a court (small claims) would rule that the airline has not complied and that a 4 day change is well beyond a reasonable change. (airlines exclude schedules from the contracts core terms - but give me a break, 4 days?)
Don't give up - this would make O'leary blush