I did think about that, but they've not sold a Dornier for years and now they've got a New Tool, why would they bother moulding an old one just for this kit! It's the Dornier I really want, the Defiant is just a bonus

With the New Tool Dornier being £17 (http://www.airfix.com/dornier-do17z-1-72.html) and the cheapest Defiant being £8 (http://www.airfix.com/catalog/product/view/id/8392/) then £22 for the doubles pack sounds about right.
Of course, I am applying common sense and should find out when it arrives, but if it's not the New Tool Dornier I will not be amused - I have reference pics of the sprues so I'll find out quickly enough!