hello mate
i had posted a thread about this, but did'nt say the previous problems i had,
i regulary get the low oil light, discovered its down to the type of driveing, and short drives anyway, before hand i had the oil level sender changed, at the advice of audi, 3-4000miles later, and get another warning, audi topped up the oil and sent me on my way, 5-6000miles later just before the service i get another warning, audi put this down to a dash problem, with no errors listed???? stange but the senior tech said this was the problem,
got a good second hand one off ebay and had it fitted, also had the milage corrected, a new unit is £300 plus and second hand one cost me £50 nice.
had the car serviced and dash fitted, and 5-6000miles later... get another warning,
took the car stright to audi who did a head check and every other check they could and could'nt fault the car.
in the recent thread i had i've learnt its a audi thing common on high mile cars, and audi are aware of this problem and changing all there oil types for older cars,
my advice is do the cheapest thing first, a oil change and sensor change
and see how it goes
also does your oil pressure light go out straight away?