Is it the sort of "Halo factor" where AMS bound travellers from say Northampton/Oxford etc are gradually migrating their business northward from LHR because of the Hassle ?
It's all about KLM and AMS cementing their claim to be the alternative to LHR R3 for the UK regions. MAN also going 6x daily next summer, as well as new double daily KL services from INV and SOU to AMS next year. So they have the UK pretty much covered.
EI and IAG are building up DUB as another alternative hub to the west.