Dont come to notts, its like harlem. Gang land shootings every night, cant cross the street without dodging bullets...
its just like any place, dont be stupid and be on your own late at night, attract too much attention to yourself, or wave your mobile phone around like its a fly swatter in the air then you'll be ok.
... i consider london to be a far worse place to live, plus, you'll only ever really be in student areas so you'll be safe, especially on campus.