cockney rhyming slang is for white van driving, jellied eel scoffing, sun reading cunts.
blag is a proper word however, it means to get what you want for nothing, usually by exercising the gift of the gab, bare faced lies and a winning smile. Blagging is a high art form - cockney rhyming slang is for neanderthals. the only thing worse than listening to some bloated cockney fuck dribbling on about apples and pears is to hear an ignorant cunt from anywhere else trying to copy them...
As to "how's your father" - look here for the official version: