IF you pay 100% of the debt, some arrangements have provision for 8% per annum simple interest to be added. Many IP's get this clause removed if it has been included.
Secured loans are not covered by the IVA and so none of your payments to your IP should be in respect of those.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014