Couldn't the outcome be "access to the UK airspace denied" only for that flight? It would have checked with an ATC and possibly landed somewhere before approach

Couldn't the outcome be "access to the UK airspace denied" only for that flight? It would have checked with an ATC and possibly landed somewhere before approaching the UK. In the case of a problem with all flights, the outcome would have been the same they eventually had. Of course I have no idea if that would be a reasonable failure mode.