2009 E70 - Diesel Fuel Consumption Issue

[sanjivsai]

Hi Everyone,
BMW X5 E70 XDrive 30dSE (2009) Mileage:15,000
I hope someone can help me.
I recently noticed that my fuel consumption had changed (just got car back from a garage). My car is using more fuel.
Fuel Mileage
Before
75 litres 280 - 290
After
75 litres 250 - 260

My driving style has remained the same, load in car is similar, routes pretty much the same, and I am using the same fuel as I have always done.
I have obtained a copy of the technical data for my vehicle from BMW UK attached with file.
The garage have said that everything is OK and it is my driving habit.
Can some help me out as to what the probable cause/s could be?

Many Thanks in advance for all your help.

Sanjiv (London)