The auto box is a peach although a slight hint of a gradient it will drop a gear, but that could be why you get such good MPG.
This is the one aspect of the Plus Four that slightly baulked with me, I wasn't a massive fan of the way the auto box seemed to change up at the slightest opportunity. Absolutely fine in towns and traffic, but a bit of a pain on the open road. But then the solution is right there at the move of the stick, go into Sport mode and use the paddles. Best of both worlds as far as I can see.
