Thank you all for your time.  You have re-enforced my deep suspicion
that since the engine is running quite good the source of the leak
maybe somewhere else.
Thanks for all the suggestions about the likely places to look for the
leak.

I did not get a warm and fuzzy feeling about the dealer, especially,
since I was not happy about the work they have done when I brought the
car there for an AUDI recall related repair (ignition switch).

Regards,

Andre

Defo leaking from the valve cover/rocker cover gasket  new one costs £15 and
the problem is the gasket goes hard and a nice new supple one will sort the
problem.

This is a common as hell problem with all Audi's and is quite simple to
replace yourself, there is also a gasket on the timing chain that could
cause the leak and is a little harder to fix but try the rocker one first
and see what happens :)

Hi,
An additional problem with my A6 is a very bad oil leak which seems to
come from "top rear".  The oil drips over the exhaust and causes an
embarrassing smell.
I asked the dealer to identify the problem.  Their diagnosis was a bad
Head-gasket.  Their estimate (incl. timing belt and water pump):
$2500.  I bought the car a couple of years ago for $2300.

Does anybody care to comment.  The car runs great, is it really the
head gasket?
What about doing such repair at home.

Thanks,

Andre