I too love cycling in London, feels very safe when the majority of traffic is moving at a slower speed than you and there is a lot to see, or in my case, discover. I go to places I couldn't be bothered to see on foot or public transport. Not that I have many anyway, but I also note that I have fewer negative encounters with drivers in busy parts of London. They simply aren't 'in control' of the interaction, as in I will be filtering past or following them in primary rather than being overtaken as on faster, less congested roads.
Edit: One thing which does really annoy me are the minority of cyclists who think they're invincible and couldn't give a t*** about anything else unless it's pedal powered and going quicker than them, which I seem to have only met in London due to the larger number of cyclists there, however you'll get those anywhere I suppose, albeit in a lower concentration.