I've been searching the forum and found some information on red-eye flights but most of the post are old so I just want to double check :)
If I'm reading the information I've found correctly it's better to take off at 23:35 and landing at 4:00, then taking off again at 5:00 for the return trip rather than taking off at 00:35 and landing 05:00 and returning at 6:00? The key here being the takeoff times being before 0:00 and after 5:00.
Is this correct?
Yes, you're correct. I find that once the route is mature and there is enough demand without competition, landing time has almost no effect. Takeoff time is less clear-cut. Midnight is a "cliff" - go over it and you're screwed. There is gradual drop-off between 23:00 and 23:55 but nowhere near as bad. The same is true in the morning. Things aren't exactly perfect from 05:00 but getting gradually better. 06:00 is better still.
I think you lose 5% 0500-0600 and again 5% 2300-2355, but 0000-0430 30-60% loss. 0445 departures onwards operate as well as 0500 onwards, when slots are short at the start of the day..
Thanks for the answers guys. Really appreciate it!