If you split up then your IP would have to seperate the IVA's. As long as you could both maintain the payments, then you wouldn't have to go bankrupt.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley. http://kallis3.blogs.iva.co.uk
There would be several options available to you, depending upon your circumstances. But bear in mind that a severe change of circumstances such as a separation, could result in much change to your income and expenditure, especially as you would be paying for separate living accomodation, so payments could only continue if they were to be affordable.