Unless you did something wrong, the dealer who sold you the car is liable for anything that could have been developing before you bought the car for six months, which is more like 184 days than a miserable 60 days. Sometimes these engines have problems regenerating the DPFs, especially if the driver switches them off mid-active regen, which then pumps diesel into the sump instead of the DPF leading to a rising oil level. A reason for the oil light could be a blocked sump strainer, preventing the oil pump from building up adequate pressure. My interpretation of the law here: www.honestjohn.co.uk/faq/consumer-rights/