Congratulations on the new purchase, I too upgraded to an E65 from an E46, what a difference!
Sorry to hear your having these issues, Starting with your codes, The DME is reporting that its running too lean at idle, this would most likely be caused by a vacuum leak, a split CCV for example, these are easy to change, take ten minutes! how the garage can justify £423 is anyones guess! I would also check the MAF, this could be giving the DME duff airflow reading meaning its not putting enough fuel in.
High crankcase pressure (little vacuum inside the engine crank case) caused by a vacuum leak causes large amounts of oil to condensate in the breather hoses and inlet manifold, this is a major contributor to oil consumption. Common causes are leaking valve cover gaskets, leaking timing cover gaskets, dipstick o-rings, split breather hoses from inlet manifold to CCV's and worst case severely worn piston rings. The latter I wouldn't expect after just 60k miles and I have yet to hear of any piston ring trouble on an N62.
Another problem that is becoming more and more common as these cars age is the valve stem seals, many people blame the long oil service intervals indicated by the CBS system, personally I agree, the oil as it ages and becomes contaminated attacks the rubber components in the engine, this mixed with the temperature cycling causes the rubber to go hard and eventually the seal loses the ability to stop oil leaking past into the combustion chamber or exhaust ports.
My car was serviced regularly at dealerships but there appears to be a window of almost 30K miles where there is no record of an oil change! needless to say im now at 105K miles and the car is smoking after idle and you can smell burning oil from the exhaust once up to temp. I am pulling my heads in the new year to address this and a number of other issues. Luckily i am able to do this work myself so its only parts and the inconvenience of the car being off the road that the trouble!
I will say that you either have to be a keen and competent DIY'er to own these cars or have some seriously deep pockets! These cars need constant attention, there is always something ready to go wrong! with the missus and two children im kept pretty busy! I love the car though, and the V8 is great, its so smooth and comfortable to drive, Im nagged weekly to get rid of it though! but its what I want, and if I had the choice id get the newer F01/02, although my budget does not stretch that far!
Anyway I hope I have helped, there are some things to check, which im sure you can do yourself. To be honest mine burns 1L of oil every 3000 miles or so, although it really does depend on how much time you sit in traffic!