Top of my head thoughts though may not relate to this car as I dont know enough about it yet.....
1. What about the inlet manifold butterfly valve thingy full of gunk?
The recirculating exhaust fumes create carbon deposits on the moving parts such as the butterfly valve on your inlet manifold. I am led to beleive that this adjust when the car is cold and warm. If its stuck in the cold position then more fuel will be used.
I had this on my Jetta around 70kmile mark and replaced the valve. The main
problem was juddering at part throttle speeds (following traffic, motorway cruising) and an increased in fuel useage was noted. Though on the Jetta a light came on on the dash.
2. MAF sensor need cleaning? assuming the CR engine uses a hot wire method. Detects air flow coming into the engine and adjust fueling.
3. Faulty lamda sensor in exhaust, detects air fuel mix and tells ECU when its running 2 lean.
4. Sticky brake caliper, more resistance thus more fuel being used.
Just my 10 pence worth
Was looking at my MPG last few days
On the way to work 8am(ish) 25miles, 5 miles A road, 15 miles motorway, 5 miles town I get about 48 - 52mph on ave
On the way home 4pm (ish) 5 miles town, 15 miles motorway, 5 miles A road I get 52 - 60mpg.
I thought it was day time temp and a rush of excitement to get to work (honest boss) that was causing the difference in fuel usage. but it turned out when I used my cycle Garmin GPS thingy that its more up hill to work and thus down hill home.
On another thought has the SEAT garage got another Exeo you can borrow for a week so you can see the difference?
Also just request the dealership to reflash the ECU with the latest firmware, all it takes is a currupt digit and problems will prevail