Ah yes. I was using the phone and did not notice the underlined, shortened link.
Your rental of a 1.0L car may be the only solution. You will have to make a serious effort to drive it exactly the same as a 1.2
There is something with the international numbers comparison that bothers me. Pèople buy these cars because they want to save money. That is one reason to drive in a modest fashion. There is at least one another reason. The price of gasoline in many parts of the world is double or triple what it is in the US. Many of these places also have higher income taxes. When you have a greatly reduced take home pay you will tend to respect your cash flow a lot more. That will almost guarantee that you use the gas pedal very carefully and it will be reflected in the fuel consumption numbers.
Another factor may be the composition of the gasoline itself. Blends are going to vary around the world.
It seems the only way to get good statistics is to do the testing in the same place at the same time with the same driver using rally car techniques to keep the timing honest.
There are probably other factors I am missing now.
Now, how can we get fifty of each vehicle for you? I am lost for ideas there...