On the vernacular point, my sister married a cockney 34 years ago. He's a proper cockney: Bow Bells, rhyming slang etc...and the difference in the way he talks, both in form and substance, compared to their two kids, especially their son, is palpable. The London accent has changed more than any other in the UK over the course of a generation. Much more ethnic influence now, than previously especially from Jamaica.
I reckon Cockneys in the 1970's probably sounded pretty much the same as their counterparts in the late Victorian era. In contrast, the pace of change in the Londoners lexicon and accent and in the last 30 years is both stark and staggering.