Hey Paul, welcome to the forum. I think that your partner would have to agree to releasing your share of any equity towards the end of the IVA if there is any but please wait for an expert to advise you. X
You would have to agree to release equity during the final year of the IVA, based upon your share of the equity remaining based upon an 85% loan to value basis. As Viki rightly states, your partner would have to agree to this from the outset, and a restriction would be placed on the property at HM Land Registry preventing you from disposing of the property without your IP's knowledge.
Throughout the IVA, you would continue to make the mortgage payments in the usual manner, and you would pay a proportion of them based upon your respective incomes.