Hire Purchase (HP) is the traditional way to finance a car purchase. You pay off the entire price of the vehicle through a series of monthly payments. At the end of the contract period the vehicle becomes your property.
The monthly payment is determined by the amount of deposit paid, the period of the contract and the sale price of the vehicle.
HP is very similar to borrowing a sum of money from a bank and paying it back over a fixed period of time, with interest. Hire purchase is a type of secured loan which are often preferred over alternative (unsecured) loans because they allow a greater borrowing limit. The term "secured loan" means exactly that, a loan that the lender can secure against an asset (in this case, a car).
As mentioned above consider financing the car over a longer contract period - perhaps a 60 month contract will make your car of choice more affordable.
The amount of deposit you are able to put down will dramatically effect your monthly payments. Higher deposit means lower payments.