[fy20]

Under EU law (this was before Brexit) you are entitled to a full refund if the flight is cancelled by the airline. If the flight is cancelled less than two weeks before departure you are also entitled to compensation of a few hundred Euro.

I actually got a cash refund from Ryanair, although it took a long time and at every stage they recommended I take vouchers that would have expired after 12 months instead.

[danpalmer]

It's still British law for now. I've not heard that it's planned to be cut in the mass-cut of EU laws, but given that it's pro-consumer it may well be.