Hi
The finance company part own the car and are entitled to the payments outlined in your agreement. If people were allowed to vary payments afterwards, you can just imagine the number of people that would try this.
Your financial and personal circumstances have changed, but this is not really something which a finance company can make an allowance for. The situation would be looked at differently if it was a mortgage for a house as lenders have some responsibility to be reasonable i.e try not to make people homeless.
If you cannot pay, then you should hand the car back. They will take action otherwise and you will incur further charges e.g. court/bailiff fees. They will win in the end and it will cost you more in the end if you delay.
Sorry Lisa that I may have come accross cold hearted but I think you would prefer a straight answer.Ask Citizens Advice or consumer Direct for another opinion.
Huckster