Gawd... from one site to another... You can lead a horse to water, but...
Jonno, "intergrades" occur within 60-100km from Gosford, and "intergrade" looking pythons probably closer than that, so I don't know where you get the "hundreds of kilometres" notion of separation... Of course, within that 50-100km overlap you will get influences of both. It just depends what you want to call them.
Scientifically, there will be, somewhere, a recognized DESCRIPTION of what defines a diamond python, and THIS IS INDEPENDENT OF WHATEVER HERP HOBBYISTS WANT TO BELIEVE... Those snakes of boas exhibit no characteristics of diamond pythons at all. I can't be bothered with this any more, but someone should contact the reptile man at the Australian Museum, ask which taxonomist's description they currently recognise (this changes as species are revised) and ask for the scientific description they currently accept as valid. Included in this description will be references to colour and pattern, with an indication of what regarded as unique to diamond pythons.
That is where the discussion should end. If you dispute the fact of that description, then you should do a crash course in taxonomy and revise the Morelia spilota ssp. yourself.
Jamie.