Did you take out a loan to purchase the vehicle, or did you buy the vehicle on finance (eg. on a hire purchase or conditional sale/PCP agreement).
If you did sign a finance agreement, the lender is jointly liable with the supplier if the goods are faulty (which they appear to be), which means that you can complain to the lender and ask them to look into it.
Also, if a fault develops within six months of you purchasing the vehicle, it is up to the garage to prove that they sold it to you in a satisfactory condition. After that, the onus is on you to prove that it wasn't. You look to be just on the borderline if you bought it in August.
Have you already contacted the garage you bought it from? You should give them a chance to respond to any complaints you have about the vehicle's condition or roadworthiness.
But if you've had no joy from them, speak to your finance company's customer services department. If they are a large lender, they will more than likely have a department dedicated to such issues of merchantability.
They should take the matter up with the garage directly.