Without the esseesse kit.

Driving like a Granny with a blue rinse on 30 - 60mph roads in eco using a feather on the accelerator  55mpg
Motorway 70mph in eco  41mpg  (there was a headwind for this)
Motorway 70mph in sport  38mpg (also a headwind)
'A' roads 40 - 50mph   47mpg
Motorway 80mph in sport  33 - 34mpg (with headwind)
Having fun on country roads with heavy braking and acceleration  around 26mpg
Overall mixed driving over 1000 miles   35mpg

With the kit on

Motorway 70mph  38mpg (no wind)
Motorway 80mph  32mpg (no wind)
'A' roads  44mpg

Haven't had it out for a real drive yet...watch this space.

All of the above were averages over at least 10 miles, so fairly comparable, apart from the headwind.

Tried really hard this tankful to make it go further, and it has. I've done over 240 miles and I've still got a notch under half a tank left. Even had a 130 mile round trip today to Chester (including a few miles at 120+ MPH  ) and the average MPG for this tank is still 40.6 MPG. Although trip B which i planned not to reset for a good 10,000 miles or so, has either reset itself or i did it by accident 

Ok so I've just filled up, i used 33.13 litres and i did 297 miles, i work this out to be 40.7 MPG (although the trip computer said 41.8 so it's not as inaccurate as one might expect) Pretty pleased with that, can't believe i resisted the urge to floor it or go over 60 for a whole tank full! If it wasn't for those few miles at 120 MPH, maybe the figures would be even better. Here's how i do the math: Divide litres used by 4.546 to get how many gallons used, then divide the miles done by the gallons used. Is there a more accurate way?

BTW don't rely on the range reading on the computer, it's very inaccurate. A few tanks ago, it said i had 30 odd miles left, then it went ------. When i filled up around 10 miles later, the tank took just over 35 litres and the tank itself is only 36 litres! I was almost running on fumes.

I've done 266 miles of hard running-in and the trip says 23.4 mpg.  It's been fun.

That's the spirit! My worst was 22 MPG when i raced an Aston Martin 
Done pretty well this tank, 200 miles so far, one notch under half a tank. I tend to get to the last few notches and then think ah what the hell, and then go back to driving fast again....talk about false economy.

Thought i'd carry on posting in this thread, it's still relevant. On my 200 mile journey today i got 47.1 MPG average. 95% in non sport mode. At one point it peaked at 51.2 MPG. I was surprised it was this high as i rarely drive on big roads where you cruise at 70 - 85 MPH i was expecting the fuel economy to decrease. Somehow i managed to squeeze an extra 100 miles from this tank too so from fill up to warning light it was 300 miles! (45 MPG for the whole tank) I guess with 5000 miles on it now the fuel consumption will only get better and better as she loosens up (along with the gearbox!)

First 600 miles. Averaged 31mpg. Few motorway slogs and a fair old bit of thrashing about on the country blacktop. Not bad.

I've now averaged out at 35.5 for my combo of mostly urban with a bit of more fun at the weekends. I'm pretty happy with that, better than the 159 managed.