You need:
Two engines
Two CPL Qualified pilots
Both of you steep ILS approach qualified
A Handling Agent
Lots of cash (£300 landing fee at peak times)
As AC-DC says, Elstree (EGTR) is a better bet. All you need there is some VFR skill and occasionally a thick skin if the AFISO gets bolshy...
Alternatively Denham (EGLD) is also convenient for the train to London.