Maybe useful to others, although its not a fix, more of a workaround.
I created a new blank PHP template and added a region.
Used that in the DA wizard and all pages created successfully.
I then applied my existing fully customised template to my recently created blanks, worked fine.
I can only conclude that it may have been the complexity of my customised template that crashed DA, or perhaps something it didnt like in the format.
I think its important to find out?
Can i post my customised template for WA to investigate please?