We convicts downunda in Australia also use these old sayings, but it is slowly dying out here too. "Digger" is not slang in either Aussie or Kiwi, but refers to our soldiers in war, but probably goes back to the great Eureka Stockade and the miner's strikes then. Just google if you want more info.
Michael Caine would have heard this type of slang every day of his life until he went to America, in various forms
Aussie
Butcher's Hook = Look (so now it is usually "take a butcher's at that me old china"
Two plates of meat = feet
China Plate = mate
Pork Pies = lies
rabbit & pork = talk (now you would say rabbiting on)
raspberry tart = fart (now just blowing a raspberry)
Captain Cook = take a look (Cook discovered East Coast Australia about 45,000 years after it was already inhabited by about 200,000 indigenous people in an area about the size of mainland America. Texas would fit into Western Australia 3.5 times and Queensland and South Australia at least twice. Even NSW is larger than Texas. WA & Qld are also bigger than Alaska. And yet Texas has about 29 million people to NSW which has about 8 million people, but about 85% live in Sydney or along the coast. Fortunately, we keep most of the politicians in a country town called Canberra so they don't get in the way.
England
Adam and Eve Believe Would you Adam and Eve it?
Apples and Pears Stairs Get up those apples to bed!
Army and Navy Gravy Pass the army, will you?
Bacon and Eggs Legs She has such long bacons.
Barnet Fair Hair I'm going to have my barnet cut.

Yeah that was a brilliant scene. The old geezers really carried this film.

Why don't you beep morons speak English?

From "Lock, Stock & Two Smoking Barrels" of course.

An aristotle of the most ping pong tiddly in the nuclear sub.

Dudley Sutton's 'rhyming slang' is a piss take of the way rhyming slang gets changed and convoluted. For example: 'Bottle and Glass' is slang for 'arse' but is usually shortened to 'bottle' as in 'His bottle's gone' meaning he's scared/he doesn't have the courage (this stems from the expression to sh!t yourself if you're scared). 'Bottle' is then rhymed with 'Aristotle' and Aristotle is then shortened to 'Aris'. So Aris-Aristotle-Bottle-bottle and glass-Arse. Dudley Sutton's character takes this to ridiculous extremes..
And just to clarify 'Bottle' normally refers to bravado/courage..(lack of) "He's hasn't got the bottle to do it".."His bottle went at the last minute".. "He bottled it" or (lots of bravado/courage)'he's got some bottle'..
However 'Aris' refers to the actual physical part of the body ("look at the Aris on that bird!"..do you want to feel my boot up your Aris?".."Move your Aris" meaning 'hurry up'.
You would never complement a woman by saying she has 'a nice bottle' but you would say "you have a lovely Aris"

I know Dudley Sutton did a bunch of drama in his younger days, but his comedy is absolutely stellar. Totally cracked me up.
Samantha
"I didn't say that. The camera must have misheard me!"

The "Trafalgars = Zombies" was 100% a joke - and a very funny one, IMHO - the joke being that the old guy was using rhyming slang so convoluted that not even his fellow cockneys could fathom what he meant and presumed he had dementia

you say that, but it still creeps in
let me have a butchers at that (butcher's hook=look)
syrup of figs (wig)
ruby murray = curry
look at the barnet no her (hair) from barnet fair
she's got a nice pair of bristols (breasts) Bristol city (titty)
jam jar - car
i'm going for a jimmy (jimmy riddle= piddle)no. 1s
I'm going to have a cup of rosy (rosy lee -tea)
i'm on my todd (alone, from todd sloane)

Rhyming slang tends to be used more in films and TV rather than real life. So that's where kettle comes from from!

most cockneys/londoners i know use it very sparingly, my old man was from london as is my mum, and they use it very sparingly. and as previously said certain phrases have only the first word said as in mutt'n (mutt and jeff - deaf ~ comic strip characters) while skin and blister would be fully said so would trouble and strife. some are not so obvious - a kettle is a watch. kettle and hob ~ rhymes with fob as in fob watch
kudos and love to michelle ryan's kyber
big blue wobbly thing that mermaids live in..

The Cockney rhyming slang used by Eric was his own version of the slang, that's why nobody understood him. Proper slang is simpler eg. whistle and flute-suit. It sounds perfectly normal to me because I live in south London, it is not exaggerated.

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Cockneys do use the slang that is why it's called Cockney rhyming slang, because the Cockneys use it, though it does tend to be used more by the older generation. They would also say apples and pears not just apples because pears rhymes with stairs.

Hmm - it does sound exaggerated. I've never heard the slang you mention, but then the English language is forever evolving.
Proper Cockneys if they use the slang at all, would only use the first word eg Going up the 'apples' rather than the whole 'apples n pears' (stairs)