Re: Is there any kind of valid comparison that has been done to other schemes?
Don't be silly. The British Government has a track record of never, ever looking to see what other countries have done before implementing a major change in the worst possible way. Examples of this are the introduction of decimal currency, metrication and the several failed attempts at introducing a national identifier.
Since the Estonian approach seems to be pretty much best of breed and that the New Zealand seems to work pretty well to is a cast-iron guarantee that the British Government will do something entirely different and/or stupid such as privatising it.