Yeah, you got ripped off. I'm from South London as well (Thamesmead) and if you don't know the dealer they'll try and rip you off at first. If you even think you're being ripped just say "Come on, you know I can't take this" and they should smile and nod and give you a proper bag. That's about a gram there, and you should be getting over THREE and a half times that amount for £20 in London.

To whoever said "LoLz ThAtZ aBouT hALf A GrAmZ" is talking out of their fucking arse. Learn to eye-weigh.