Why is that a fallacy?
If you look at the putative billions in lost trade that arise to the UK because there isn't a direct flight to somewhere or other, the inconvenience caused by consolidating flights should be trivial in comparison. If it's so many billions, the state could pay the market rate for slots that airlines are deprived of.
Airlines could be given a few years to acquire 77Ws/748s/380s for the role.