hi, I usually go to Cmaden Market when I go to london, and i found it great. I never bought of the street instead I approached a stall holder, asked him could he point me in right direction.
He said he'd get it for me, the only thing was I had to hang around the market for about a half an hour, but by god was it worth the wait, it was the smelliest skunk. I actually felt very uncomfortable smoking it in hotel room, it was stanky!!!, so I walked around the parks of london, with a big fatty strapped to my lips

In the market, the guy i used sells rastafari t-s, has braids, not dreads. There are a few good gys there, who wont fuck you over.

Hope this helps somewhat.

rastagal.