Thanks for your question. this is quite difficult after this period of time. Assuming this is a consumer contract i.e. you did not buy for a business , then your wife is entailed to goods that are fit for the purpose and are of reasonable quality taking into account age and price ( e.g.whether they are new and or second hand) and are as described under the contract. Where defects appear within 6 months of purchase then they are deem to have been there at the time of purchase putting the seller in breach of contract. However after 6 months you need to prove the defect was there at the time of purchase. In the case of moth leaks you mentioned it sounds as if they were outside the 6 months period so the burden of proving they were manufacturing defects or were present at the time of purchase falls on you. You will therefor need to get an independent engineers report on the problem if you are to sue. Your rights if you can show the defect was not cause dafter purchase continue for 5 years ( in scotland 6 years in england) after purchase and you are entailed to ask the retailer to repair the car or replace it but the retailer can refuse replacement and offer to repair it instead. If they fail to repair it in a reasonable time then you can rescind the contract and claim damages. If you were wondering if you could reject the car and ask for your money back then no I am afraid no because this can only be done in a reasonable period after purchase which in the case of a car is usually a matter of a few weeks .

So in summary in theory you can claim rescission and damages but you will need to produce evidence to show the reason for the defect and that is has not been properly repaired which may be difficult. Your claim is against the garage who sold the car not against the manufacturer.