Hi there,
Sorry to hear about your situation.
You will need to look at the documentation provided about the PPI as this should detail what the insurance will cover in the event of a terminal illness. This could be to cover monthly payments, or to pay out to cover the remaining finance.
Until the finance is paid, you can't really sell the car, which is realistically your only option and buy another car.
Other options instead of buying a car would be to lease, or rent an automatic.
If you can provide more information about the PPI we may be able to offer more advice.
You should be able to contact Welcome to ask them about the PPI directly and what options you have.
You could also visit your local Citizens Advice Bureau with your documentation and they should also be able to advise you.
HTH
Sparky.