Audi Problems

At 1 litre per 1000 km your engine was already consuming too much oil, at double that rate of consumption it is way too much. VW/Audi engines have a reputation for using oil and need to be checked regularly to ensure you don't inadvertently cause damage by letting it run low. You could try appealing to their sense of goodwill and ask Audi to cover part of the cost of repairs, but as your car is seven years old I don't believe you have much chance of success.

In my view buying a used European car is risky, they're expensive to service and repair, and more things tend to go wrong with them as the kilometres climb. 

You're more likely to hit snags with them than you are with less exotic cars from other parts of the world. With Audis you should try to ascertain if they are using oil, and you should thoroughly check the operation of the automatic transmission. 

Once you have chosen a car I would urge you to have it checked by a mechanic experienced in Audis or VWs.

From your description I would agree with you that it doesn't appear normal, although road testers talk of mild turbo-lag at takeoff. Mild turbo lag doesn't seem to equate to extremely sluggish, but it would be worth your while to drive other similar A5s to get a feel for them as well. Perhaps your dealer might be able to arrange for you to drive a demonstrator.

Your budget limits you to older models, such as 2008/2009, which will have done 120,000 to 180,000 km. I am loath to recommend buying one of these cars with such a mileage on them; you would be heading the period of pain when you are quite likely to face increasing and expensive repairs. If you were to choose to buy one I would go for the Discovery. I would also urge you to have the car you choose checked over by a specialist mechanic who knows the brand intimately. Instead of the European models you are considering I would suggest you also look at something like the Toyota Kluger, which would likely to be more reliable and less expensive going forward, and your budget would stretch to a later model.

Audi was caught up in the same DSG automatic transmission problems that afflicted VW, but you would hope that those problems have been sorted out on the later models such as the 2015 car you're looking to buy. Apart from that doubt the A1 is generally a sound car. As for servicing costs the A1 is about the same as the VW.

That's a rather subjective question that's almost impossible to answer. It also depends on what you call fun. Both would be fun to drive, but if I were to make the choice purely on the driving experience I would choose the BMW.

I don't think there's much that can be done, apart from paying up and having the test done. The car is a 2009 model and I doubt that you would get any joy out of Audi regarding the cost of the test. VWs and Audis are renowned for using some oil, and that's one of the risks of buying a used one. What you need to know is how much oil it is using, and if that is a problem.