Nothing more than sensationalist crap.
If you look at the GA procedures for LHR then you will see some of them do turn accross the SIDs'- Standard GA procedures seem to have been followed. How can you judge that an aircraft had to turn through 90degress for avoidance from the cabin??
Many things in your story smack of passenger ignorance and jumpimg to conclusions regarding what is actually taking place in the flight deck and what you are actually being told/second guessing.
For instance, how xan you judge 5oo' separation from the cabin? i have been a pilot for 10 years+ and i reckon i couldn't be that accurate...
I would hazard i guess that the aircraft didn't head out over the channel to use up fuel as you say, but merely was vectored clear of the London TMA in order to complete the checklist.
Oh and don't get me started on that nonsense about losing the rudder and having to maneouvre by rolling only!!!! Eh???