There is one rule to driving in London and that is "Show no weakness!" Think of yourself and yourself only and you will be fine. Never ever ever try and be a considerate driver in London. It just isn't worth it. Besides if you sit there being nice to people you will never get out of your parking space let alone accross London. Oh yes and DON'T stop for pedestrians.
Up where I live in holiday time though isn't too bad driver wise. It does however happen to be roundabout central. Seriously I don't think they could possibly have squeezed more roundabouts into one town! Oh well Milton Keynes maybe!
All thre worst drivers do seem to be concentrated in Norfolk though and on the M42! Bloody maniacs!