Hi Diane and welcome to the forum
Your car would be safe, as it is owned by you, but your husband's share of the equity would have to be addressed by you both agreeing to remortgage the property during the final year of the IVA, to a maximum 85% loan to value. Your husband would have to introduce his share of the equity to his IVAm subject to a deminimis sum of £5,000.
The IVA could also affect you with regard to your income, as this would have to be declared under the terms of the arrangement. If your husband has all of the debt, and you have no debts, creditors will assume that you have benefitted from these borrowings and may ask for you to introduce your surplus income into the arrangement.
It would be sensible for your husband to seek the advice of an insolvency practitioner to ascertain what options are actually available to him - as an IVA or bankruptcy are just a couple.
Regards, Melanie Giles, Insolvency Practitioner