Naughty boy
the night noise restrictions at heathrow are quite clear.
ATC should not have given you line up clearance especially if there were some on approach. having said that ATC might not of known whether you were going to infringe the night noise ban or were exempt ( some aircraft are. i wont explain as its too complicated)
the Ops Duty manager should have told ATC not to let you depart before 06:01 ( local) .
the Ops duty manager would have got a bollxxxx as well as he shouldnt have let it happen. I think I know who it probably was !!!