LTNman
Say the station is a mile from the terminal this would make it 5,280ft away, add 5.88% and that would add 310ft or 94metres. So a docklands light railway type train could get the the terminal.
Back to the question do you go over or under taxiway Alpha?
Well, that is great research which should have been done 20 years ago so that the line could have been done at the same time as the new approach road. THEN they could have done a 'cut and cover' tunnel that would have been sooo much cheaper. But (as I boringly repeat) this is Britain.