Runway at Aberdeen is too short as well.At M.8 there is a chance of not getting a favourable cruising level as all the faster stuff whizzes past above.
I used to watch Qantas 767/300 depart every night out of Hong Kong to Melbourne,Brisbane,Cairns which was about a 9 hour sector.They took about 2500M to start rotating,and on a bad night a whole lot more.Aberdeen has 1830M.
Mind you a few people are saying that even a refuelling stop in Gander,or wherever, is better than Heathrow.