I had my A4 went in for a survice last month , i have drove 2500 miles when the oil light came on, no oil leaks no sign of burning oil , but i had to put in 1.75 lts of oil , why never before

Sure sounds like a leak to me, and it could be burning it. You just do not see it while driving. Could you look under it for wet spots or places, no wet places its burning it..

Seriously check the type of oil you are using refer to the factory hand book..before you do some damage..

I have seen this before with European vehicles..