A keen car person should be able to keep top-ups down to 0.5litre - check it frequently you know it makes sense, I'm not suggesting that you do the following - but - its a mug's game waiting for the low oil warning monitor to prompt you!
 
Hello, I only bought the car on Thursday and the oil was first thing I've checked.. but yep I plan to check if often, and its just nearly taken the 1 ltr.. thanks for your help :D