Hi Ebbie.
Berts , got it Cockney slang is a rhyming slang.
For instance................................................. Apples and Pears=Stairs.
                                                                               Bull & cow = row ....................(Argument )
                                                                               Sister = Blood Blister.

So East enders would use a mixture of Rhyming slang and ordinary words to form a sentence.

For example
If I was to say

" I had a row with me sister and she fell down the stairs.

In Cockney Rhyming slang that would translate has.

'' I had a Bull and Cow with me blood blister and she fell down the Apple and Pears.

Kind Regards
Pierre.