From earlier posts Stepchange do not appear to have the interest in PPI as other firms, but this could have changed. Many claims companies will not proceed when they are aware of an IVA as, often, they get cut out of the loop when the refund is made direct to the IP, rather than through them to enable them to take their fee.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014