Q3 35tdi quattro - fuel gauge issue?

We took delivery of our brand new Q3 last year. Since then we have had issues with the fuel gauge registering 50-60 miles remaining but the car stopping dead (once in the fast lane of the motorway) and having to be recovered to the local garage.
Each time they have told us that the car has run out of fuel and they have re-set the computer. The time it happened on the motorway and the car was recovered by the police and Audi agreed to pay the £270 it cost me to recover the car from their compound and we have now started to take a can around with us.

Last week I was driving along showing 60 miles remaining, when the car suddenly died again, I went to use the can in the boot but it was empty (my wife had not told me she had used it the week before!).

I have spoken to Audi as I find this extremely frustrating , but they are now telling me that it is not their issue and is down to driver error as I should not let this particular car's fuel level drop below 100 miles remaining due to the DPF.

Nobody has mentioned this to me before on any of the occassions the car has been into the garage (with the same issue) and if driver error was the cause then I find it strange that the first time it happened they paid the police recovery and storage charges.

Every other car I have owned tells me there is no fuel, when there is actually some left but this one seems to be the other way round according to Audi.

Has anyone had experience of this please and can maybe give me some advice?