It should take a couple of months ( maybe three) for the offer of a settlement to be put to the creditors. After it has been accepted and the monies paid over the final administration period is the same as if the IVA had concluded at the scheduled time. This can be anything from 2 months to a year, depending upon who you are with and how they are treating PPI.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014