Auxiliary drive belt/crankshaft pulley

My car is a tdci mk3, which I have had for over ten years. My dilemma is that I only intended to keep the car for a further eighteen months to two years, but I need to replace the auxiliary belt and everything that comes with it. The cost for quality parts which I think is made from a company called gates is over £100 then add the labor. I do not want to buy parts of a lesser quality, but I am thinking I am only keeping the car for another eighteen months or so. Would buying lesser quality parts still last for that period of time as opposed to buying good quality for only a short time?

Thank you in advance for any advice.