I would avoid 'Eco' mode for any length of time until the car is run-in. I don't think it does any harm, but it's just painful. By the time my Parents TwinAir had done about 7000 miles, Eco mode was nearly as good as standard mode was when the car was new. The TwinAir's really do improve once they've done a few thousand miles.
The MPG in our 500 was always above low 40's, even when brand new. However it doesn't have the added 4x4 gubbins of the Panda 4x4, which i'm sure accounts for some of the typically lower average MPG results when new on the 4x4.
Once you get those few thousand miles under its belt I think Goudrons result sounds about right - our 500 used to get mid-late 40s to the gallon, for reference.
Just one question - which socket have you plugged your phone into on the Blue&Me port - USB or AUX? I'm currently struggling to play Spotify in my car through the USB port and wondered if the AUX cable I've ordered today might sort it? Thanks!