Thanks for the link. My reading of the article is that whilst McKay junior was acting for Nantes, it seems it was McKay senior, who had contractual relationship with Nantes, who organised the flight. The article is silent on whether the flight was requested by Nantes, or whether McKay senior did so off his own bat. Either way it’s been established that the transfer was completed.
Another uncertainty is if Cardiff, who offered to pay for a BA scheduled flight, were aware that Sala was going by private charter, and if so, did they have a duty of care?