I have booked and fully paid for a private house through booking.com on Tenerife in early April. The owner has agreed a full refund with them but booking.com want to deduct 20% cancellation charge. I have not pressed the cancellation button as I believe if I wait surely they will have to refund me 100%? I have registered my complaint with booking.com saying that my flight has been cancelled and the State Of Emergency in both our countries surely means a refund of 100%.
If you have booked the flight separate from the accommodation I think it's not their problem if you cancelled and they certainly can't resell it now. They may suggest you try your holiday insurance. If you paid by credit card you could try to claim from your card provider. If on the other hand you'd waited for booking.com to cancel you'd be entitled to a refund (or maybe vouchers if the expected law/rule change goes through)