PPL pilots take note - ATC is not a big bad monster. They are here to help and assist - as YOU must do when given a direction.
And they are fantastic! Ok, maybe a little scary, but the guys and gals you speak to when flying the heliroutes and in particular crossing LHR are some of the busiest in the country and are unlikely to want to divert 300-odd pax in a Boeing because I'm numptying around in me R22
I think it also bears remembering the privelege of being able to operate over London as we do, and not risk throwing it all away by bad airmanship, a fact recognised by the controllers and clearly by many posters on this subject.
That said, if you fellow PPLs have not done it, get yourself an instructor and a helicopter and go for it - the experience is unforgettable!