As far as I was aware, there is a difference between a NIL TAX IPA (what you have), and a standard IPA (which is based on your I&E).
The Nil tax comes in to effect as soon as you go BR, when you get that set of paperwork and have to signed the form about tax and national insurance. This is the point where you sign regarding nil tax IPA.
The I&E wouldnt count against the nil tax IPA, but it would mean you didnt get a standard IPA on top of the nil tax. to the best of my knowledge, all bankrupts paying tax through PAYE are liable for a nil tax IPA automatically for the ta year they go BR.
Mine was early march, so no nil tax put in place (no time), but they want me to do a tax return at the end of the year to claim it back for the OR.
TBH,I think you are going to have to pay it back as technically you agreed to it, and it is standard procedure to get a nil tax IPA. I'm really sorry.