What does the service book say? Im sure you must be due a service by 15000 miles!
If you get a service done they will drain the oil thats in there at the moment then fill it up with new so you wouldnt need to go to halfords. Do you regularly check your oil? You should do really as the oil light usually comes on when its well below what it should be!
If it is due a service, it might be worth buying a litre of oil from halfords / a service station to top it up and make sure it doesnt die while waiting to go in to Renault. Your handbook should say what grade of oil to use, but you cant really go far wrong with a 10w40 if its an emergency.