It depends.
From experience: 
     If you cruise on the motorway in no particular hurry you'll see > 36mpg at a GPS indicated 70mph on the computer, 
     At a GPS indicated 80 I guess (because I wouldn't know  

)you'll see closer to 32mpg 
     If you are gentle and tool around on A roads and B roads you'll see 30-32mpg
     In town you're likely to see mid to high 20's - depending on traffic
     If you drive it hard on non-motorways low to mid 20's mpg...
Mine is standard.
Given the perrformance available I think it is pretty good on fuel but on large throttle openings will see it drink quite heavily - not a problem for me. 
I suspect my average over 32,000 miles (I picked mine up a year ago today) would be around 28-30mpg although I haven't measured it probably 75%-80% of my driving is on motorway/dual carriageway.