Although I highly recommend using the services of a professional driving instructor, it is not necessary to use a driving school car for your test. If you are planning to use your own or a family member’s car, you MUST make sure of the following:

The car MUST be roadworthy, and preferably clean inside and out.
The car MUST be insured for your use.
Seatbelts MUST be properly fitted, front and back.
Although dual-controls are not required, you should provide a rear view mirror for the driving test examiner to use. You can get these with suction pads from any car accessory shop.
The car MUST be displaying L-plates front and back.
Finally, please be sure to fill up with fuel before arriving for the driving test!