I remember when Schiphol used to advertise itself as "London's Fourth Airport". So something 'local' like Oxford can probably claim to be a London airport just like London-Luton and London-Stansted.
I do worry about the potential for increases in controled airpsace in the area - that'll further choke the remaining Open FIR traffic into an ever smaller space. To the East of Brize on a sunny day you'll find hundreds of GA, Microlights and gliders all in the same area. If that area is then shrunk further then the collision risk must grow quite significantly.