If I was a journo I would hope I had better stories than low flying helicopters to work on! (mind you given the state of the british media prob not).
Anyway, as a matter of fact I do live near bishopsgate!
re: "could have been at 500ft?" - yes my height estimation could be out - true. Can't be sure. I'll take my camera next time and post a pic! (only kidding, I'm really not that bothered).
However, even if it was at 500' I'm still curious if private heli's can get special VFR in the Heathrow zone on a regular basis??