This is something you would need to discuss with your IP. Critical Illness insurance is designed for two main purposes: Sorting out debts, sometimes paying off the mortgage and then for living with the illness (making life easier) and paying for any adaptations needed in your environment or lifestyle.
Obviously your IP would have an eye on the first one --- he might be ameniable to using part of the payment as a lump sum full and final offer to get the IVA cleared ( one less major stress on your husband) and leaving the rest to make going forward easier.
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
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