First, I would take what you have been told with a large pinch of salt .... it needs clarification. This does seem unusual, as in most cases it is "No finance ... no car!"
You will not be able to get finance at reasonable rates, although Moneybarn does, sometimes, lend to those with bad credit, the rates are high .... if you go down this route, get written agreement from your IP.
I would be inclined to let your family purchase a car --- the car can be in your name on the V5C as this records the legal keeper, not the legal owner. If your auntie loans you the funds I assume the IP will allow you to make repayments -- if they stand by earlier advice -- again get this in writing BEFORE doing anything. If your uncle gifts you a vehicle you can always repay him after the IVA is finished.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk