The IVA will still be on your file and some providers will turn you down. However, many have managed to get new contracts, even while the IVA was still active, so it is not impossible.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014
I took out a new contract for my daughter's phone while in the middle of my IVA, and have just upgraded her phone on a new contract as hers was up for renewal.