An interesting point might arise where commuting time was within limits when you joined but due to traffic increases or changes to road systems it becomes excessive. Can they force a move under those circumstances?
Even so I struggle to believe it is possible to safely work an EJ roster with 90 minutes clear road travelling time even if the car park is right next to the crewroom rather than a half hour bus ride away. By any sensible measure Oxford to Gatwick is surely far too far for safe, fatigue free commuting.