I was told once BA have accepted the ‘unfit to fly’ note you just need seat availability and not Avios availability.

The policy is called ‘mid travel illness’ so presumably doesn’t help if you get sick before your trip starts - one for the travel insurance.

I’m waiting on BA to confirm acceptance of the unfit note, the slight delay appears to be frustrating my insurer a little.

In any case my partner is still not feeling up to flying so got time for things to play out.