With my pedant's cap on (and as you know, I do have one) the Cockney quiz completely misses the point of rhyming slang, as just about everyone does these days.
The object is obfuscation: e.g. the Cockney Rhyming Slang for hair is "barnet", for face it's "boat" and a hat is a "titfer". Completing the rhyme is revealing the code!
~iw
