The new age of sleeper trains
spectator.co.uk
spectator.co.uk
It being a relatively short distance this makes sense to me.
But with COVID, airports added an extra hour of recommended time for both domestic and international, and security is staffed for the median, not the peak, so it looks like we can expect no improvement there.
Random dates in July: £270 sleeper, £62 flight
Perhaps demand is from people that don't like flying?
Basically for people who would fly in the evening and stay at a hotel in order to be ready at destination first thing in the morning.
Of course, within the UK distances are so short than you can also be at destination early in the morning by flying very early...
So, really, people pick the sleeper train for the experience.