I have a Tech Line Nav 1.4t manual and according to my trip meter for a recent trip :-
Covered 201.4 miles (about 190 of these were one trip, mostly on the M40/M25)
Fuel consumption average 50.1 mpg
Average speed 49.4 mph
This appears to be what I expected from this car, my normal running about town confirms low to mid 40's, usually 42/43 mpg.
Faults and Technical chat for the Vauxhall Astra K