The advertised vs. real-world mileage discrepancy that Americans are becoming very familiar with – see Hyundai/Kia and Ford – are not limited to our part of the world. Over in the UK, Audi is involved in what could be, in the words of The Guardian, a "landmark case" by the Advertising Standards Authority (ASA).
The crux of the matter is whether or not car companies can say what the official government miles per gallon figures are without also saying that they "may not reflect real driving." In the ASA case, Audi admitted that the official numbers for the A3 1.6 TDI (68.9 mpg, on the lenient European cycle), "did not give an accurate representation of the actual fuel consumption which could be expected from any particular vehicle and were provided only to enable comparisons between different vehicles or models" but still wants to use them in ads because consumers are aware of this. The ASA says the not-so-accurate-representation is not, in fact, obvious to buyers, and therefore Audi needs to put up qualifying asterisks – otherwise it runs afoul of the Committee of Advertising Practice (CAP) Codes. If the case goes in favor of the ASA, all car ads in the UK would need to have these disclaimers.
Last year, the ASA took an ad for the Chevrolet Volt's sister vehicle, the Vauxhall Ampera, off the air because the driving range claim was found to be misleading.