A mix of Californian and Jamaican (I live in England, it's pretty popular.)
Are you one of those white kids from Kent that speaks like a Croydon crack dealer? All "Mandem" and "Bare Shank?"
I don't really use slang normally, I accept my middle classness. Sometimes for a joke I'll use American slang, I'm pretty good at accents so I mix it up.
Maybe a couple of English ones.
Quid - fairly standard
Tidy - to describe an attractive lady, or anything good in general
Spawny, jammy - Lucky
Can't really think of any others.