Here's a prediction for you all.
NOTHING will happen, apart from perhaps a couple of fist fights in a back alley.
The media yet again have hyped all this to extremes 'London might get smashed' - 'we're hearing unconfirmed reports that the protesters have nuclear weapons' etc and of course every minute another 'breaking news' story.
Personally I wouldn't worry and if I was in london I'd go around doing my business as usual.