I need a letter from the IVA company so my car finance can be released but my IVA company has closed down and are transitioning to another company who say I have to wait until my old company has transitioned I don't think my finance will go ahead without that letter
You are entitled to near uninterupted service during the changeover -- after all they do not tell you that you need not make any payments during this time. Write directly to the new IP requesting a response within a given time frame. If they fail to respond you can escalate the complaint to their regulatory body.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014