so does that mean if they go bust i would have a free car

Im no expert but essentially:
The car belongs to the finance company until you have paid them back all of their money. Even though the V5 will be in your name its not your car.
Finance is a big big big gamble.
For instance if you buy a car for £8000. Finance over 3 years. They will probably charge you somewhere in the region of £1200 over those 3 years. Making you pay back £9200 for the car that was listed for £8000.
Then you need to take into account the fact that the price you pay from a dealer is normally a bit expensive compared to buying/selling privately.
Then the depriciation of the vehicle. As most finance companies will only give you finance on fairly new cars, the depreciation will hit hard over the 3 years.
All this means that say after 1 year of the agreement you want to sell up, you will probably find that you owe the finance company more money for your car than it is actually worth to sell on.
Most companies wont charge you for the interest you havnt used if you settle early.
So if the company went bust i would presume you would owe them whatever it is to settle the agreement. You may find that the car doesnt cover that.