You will also need to factor in statutory interest before the debt can be fully repaid. Your new payment will not be dictated by the amount outstanding, but will be your full disposable income .... if this hits the full original debt amount, fees and statutory interest early, then the IVA will conclude early.
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
A full review of income and expenditire is required to ascertain the affordability and your new monthly payment.
Moving back in with parents may mean no rent but has it increased travel costs to work ? Has it reduced other outgoings i.e food costs ...you need to ensure a full review in done for you.
Sharing from experiences of dealing with debt
There is a solution for everyone .... Just need to stay positive !