Mine has been as thirsty as yours, but i managed to find an oil leak on the back of the rocker cover.
My cambelt and tensioner were replaced by vw a while ago, and since then my oil usage has more then doubled.
I found half the small screws that secure the rocker cover had either become loose, or from the pressure inside the rocker box forcing oil out , down the back of the engine, not easily visable, unless you have a look on the drive shafts for any signs of dripping.
As said, it might be worth looking, cus it may be an external leak rather then excessive oil burning.
This i discovered, only a week after VW had my car for its annual service and
didnt inform me that i had an oil leak
.
Might be worth a look.