I have asked once or twice before and never been successful. Vueling generally will do anything (i.e. do nothing, ignore emails, reply with standard form not actually answering query, etc.) to avoid paying EU compensation or provide refunds of any kind.

If the flight isn't imminent, you can hang on and hope for a serious schedule change and then request a full refund when you might have better luck. Coincidentally I had that happen on a RAK-BCN, although booked as an IB codeshare, and I received all of my money back.