Many people in an IVA get student finance with the agreement of the IP. The problem here is, possibly, not the finance itself, but the fact that you haven't discussed it or got the permission of your IP.
There is always the chance that they will notice at some point, so maybe it would be an idea to tell them and get it sorted out now, rather than wait to be found out later, which might be worse.
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