I share the view that the OP may not be eligible for refund of the difference in miles between F and C because the OP asked to be rebooked from EDI and refusing to travel on the delayed BA57 in F (departing LHR this morning). And before anyone starts arguing about downgrade, it is def. not a downgrade in a situation where pax requests to be rebooked to another carrier without F. Anyway, the OP and party seemed happy about traveling w/ QR in J (but of course frustrated that a member of the party wasn't able to travel) so maybe better to let it go (in particular if booked into QR revenue class).

Yes, a cancellation and refund of Avios and taxes etc would always have been an option, but this was clearly not what the OP and party preferred. Neither was apparently rebooking into a later date convenient to pax.