On the subject of less than respectible rhyming slang terms in common usage, one could add:

"Wick" (as in "Gets on my wick") - Hampton Wick : Prick

"Cobblers" (used to mean nonsense, rubbish) - Cobbler's Awls : Balls

"Bottle" (moral fibre/courage as in "Lost his bottle") there is some dispute as to whether this rhyme (Bottle and glass) relates to 'class' or "arse" (relating back to the Georgian/Victorian term 'Bottom' to convey solidity or moral substance).

As to the original use of rhyming slang It is said that it was devised for use by the criminal element of society, but why would they drop the almost impenetrable cant for a 'code' that was fairly easily broken by anyone with a similar background. Personally, I feel it was more likely the domain of 'cheapjacks' and 'patterers', those who made their livings selling cheap or inferior goods, often using wit or a quick tongue as sales tools (think of the salesmen at the likes of Petticoat Lane Market in London.

W