It would be worthwhile advising your IP to get their consent. While I doubt the IP would have a problem there is a possibility that this would create an early redemption penalty and thus reduce any equity available in month 54. It would therefore be worth getting IP approval.
There should be no problem, but, during my IVA, I always took the line of informing my IP of everything, so there could be no nasty surprises or misunderstandings.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014