Stn-man
Those were similar timings to the FR Blackpool flights.
It was no problem at all getting very healthy loads from the Blackpool end, for people spending the day in London, but it was difficult persuading people in London to get up around 4am and not get back until midnight.
One of my work colleagues used to travel down from London and be in the office before most of the local staff. He generally finished around lunchtime, so would have been hanging round for hours waiting for the return flight, so ended up travelling back from Manchester.
It might work better from Manchester, although FR had an advantage from Blackpool as there is no proper rail service since the grey bearded wonder withdrew the direct link..