Hi Grunger, Hi Jo,
I think cockney rhyming slang is spoken more by "faux" cockneys and in poorly scripted films by the likes of Danny Dyer - rarely have I heard it used by native east enders.
There are exceptions, of course, and I've definitely known of people going for a "ruby" after getting a few "sherbets" down their "gregory" - I've even been one of them:-)
Like you say though, the most commonly used term is probably "butchers" which I've heard used by people of all regions.
I remember when I was a young teenager my friend had a poster on his wall with all the various terms - would have come in useful yesterday when trying to parse 24d.