You're partner will be affected credit wise as you are joint account holders. Which bank is it with? Some banks do not like an IVA and will close down accounts. If you have an OD facility get it removed and I would also look at opening a new account with a non creditor bank (Co-op come recommended).
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
As Kallis says, some banks react badly to an IVA, others are OK with it -- but you will not be allowed any overdraft facilities. You are associated with the joint account holder, financially, on the credit reference files, so the other party's credit rating might be slightly impacted by that association. The same applies for any joint accounts you might have.
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