If one of your loans is in joint names, then it will be included in an IVA but your partner will then become liable for the whole amount as you are jointly and severally liable for the debt.
Your partner would have to continue paying at the full rate.
I recommend that you take some professional advice. Visit www.iva.com for a list of companies and reviews and you will receive free and impartial advice.
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