The maximum repayable in any IVA is the balance of the original debt plus fees, disbusements and possible statutory interest. However, when repayment is made by way of equity release statutory interest should not be added. So your assertion is correct.
The amount to be released will also be affected by the ceilings imposed on the repayment of the remortgage, i.e. that it cannot exceed 50% of the IVA repayment and the term cannot exceed the original term or state retirement age, whichever is sooner. So, the equity release cannot increase your current mortgage payment by more that £76 per month.
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