For health / fitness-to-fly reasons I've just had to cancel an Avios reward trip halfway in, e.g., the return flights only. I did this well more than 48 hours ahead of the return trip via MMB on the app, and received an automated cancellation confirmation (lacking all specifics obviously). 50% of my expenditure for the trip comes to 52k Avios + US$562. Have I a hope of getting any of it refunded?