Hi Jason and welcome to the forum.
Sorry to hear that you are having problems.
You could try this company for a car:
http://www.duncton.com/jsp/index.jsp
APR is high, and you will need a deposit, but you can get a car.
I'm afraid the inheritance is classed as a windfall and will be required to be paid across to your IVA.
Unfortunately, things like holidays will have to go by the board until your IVA is over unless you can make any savings from your allowances.
If you really feel that you should not have entered into the IVA because of the restrictions, you can let it fail and either go bankrupt or go into a debt management plan.
Which company are you with?