As long as you dont wander too far south ( or east for that matter ) you should be cool in London. West London is likely where you will be heading and I wouldnt worry too much about being mugged there. London's crowds are beneficial in a way. And unless they have a gun or knife, fight back in any case. I just dont get it when people so easily hand over there belongings to something maybe only an inch bigger than them.

Im also in the same situation an Cz, Ive lived here all my life and in a particulary bad area in Southwark and have rarely been in any trouble. Be street wise my friend.