Yes, you are insured - just not to drive or for the vehicle to be moved off your property. It would be covered for Fire and Theft only. Should the vehicle not be roadworthy, then your insurer may not pay out. Insurers will generally view the MoT as evidence of roadworthiness, but this is not always the case. Your insurer would still have to cover you for third party risk under the Road Traffic Act 1979, but they could seek their outlay if you have failed to follow the terms and conditions of your contract.