File with the Stansted Tower address as stated above. Plan both routes (through and around) and then ask Essex Radar as early as possible as it will depend upon the traffic environment and controller workload at the time.
Never been denied yet, but make sure you know where VRPs are as you may have to hold to get across behind landing traffic.
Make sure you bring your best Radio patter as if the controller has confidence in your ability to fly you’re more likely to get worked through over a stuttering, mumbling train-wreck where he has to ask for everything he needs.