As it will be part of your income, then yes this will have to be included, and as you will not be paying national insurance contributions past the age of 65 you may find that this will also increase your contributions.
It really depends upon the terms of your proposal, as there are many differing clauses relating to additional earnings in circulation. If your IVA was proposed in accordance with the IVA protocol, then you will be required to account for 50% of the increase in your net income - which takes account of additional costs.
