For all of those trying to acquire a cockney accent (why for goodness sake??!! Oh never mind) PLEASE PLEASE don't go overboard on the slang side. The odd slang word gets mixed in but no-one walks around absolutely packing their speech out with these words, honestly. Some are used a lot, some are used a little, and many are virtually never used. You'll sound ridiculous if you keep forcing loads of these expressions in to your conversations non-stop. Real cockneys don't, so 'leave it out'.
For example: "they use the synonymy like gray hound =one pond so if you ask some one about the cost of something he will reply it cost gray hound".
No they won't, they'll say 'a quid' like everyone else. Which is also slang, but the sort that gets used in reality all the time.