So many of these new cars on the road are financed via PCP (a way of making it seem like the loan is mlre affordable) or Lease (so you never own the car).
With PCP you pay a deposir, then pay a monthly amount then pay a big balloon payment at the end if you want to own the car. This method of finance has given car salespeople the opportunity to sell people cars they can't afford, as ot reduces the monthly payments by way of the balloon payment. You pay interest of the entire value of the car (including balloon payment but minus deposit) for the duration of the deal. So even if you don't buy the car at the end you will have paid full interest for 3-5 years.
If you do this, take GAP insurnace. If you don't and the car is written off in an accident or stolen you will still be liable for full value of car plus (I think) interest for the duration of the agreement. Insurance will only pay you the value of the car at that point in time. In other words you could be left paying for a car that you no longer have.
Equally, if you lose your job... in PCP or a Lease you can't just hand the car back because you can't afford the payments, you will be subject to all kinds of penalties. On the other hand, if you don't keep up with payments then they will take the car and you will STILL be liable for the penalties. So no job, no car and still huge debt.
A personal loan from a bank may be the most economicsl way of buying a second hand car. You will normally get a better interest rate (I have an excellent credit history so would have got 3% vs 9% from car dealers on HP).
If you buy second hand then generally you shouldn't be too out of pocket if the car was written off or you had to selll it as you can pay off a loan early without being liable for all remaining interest. There might still be a slight discrepancy depending on the rate of depreciation but it will be significantly less than PCP. The more you can pay in a deposit the better protected you will be.