No idea I'm not a energy saving expert nor would I like to make a comment outwith what I know.
Cladding is a effective way as has been shown with the thousands of buildings that have it, if installed correctly with the right safety measures in place. Without knowing the design of the built I cant say if there would have been other competitive methods.
As I said the chimney effect doesn't happen in cladding systems made to spec, look it up, do your on research don't believe me or anothers word on the internet.
The cladding was never done with "energy efficiency" in mind, it was to appease the higher class londoners that wanted them to look nicer.