I don't think there is any debate that the reason for the prohibitive entry qualifications is the tight time scale for air-side passes.
If I was an ambulance chaser, my argument would be that it was Virgin's poor planning, in making it a competition with a tight time scale that has caused the discrimination against non-UK citizens.
I can see that argument that lots of competitions have entry requirements - e.g. those with alcohol prizes are only open to over 18s.
The difference is that it would always be illegal to supply alcohol a a prize to under 18s, but here the time scale issue is purely of Virgin's making and - if they had announced the competition some weeks / months ago, with the prize trip to be taken on a date to be fixed, the air side pass issue could have been sorted.
As I have said, I hope nothing is made of it, but I enjoy debates like this. We used to have lots on here, but they seem to have died away.

):
I too hope a V-Flyer wins and they got lots of photos.
Nick