Car accident insurance advice?

My husband recently had a car accident. When taking a turn on a dual carriageway junction the trailer on the vehicle beside him went into his lane and tore the front bumper off our car. He got the insurance details from the other driver and their insurance company is the same as ours. We brought the car in to the assessor and they strongly advised that the car not be driven. So the car is with the insurance company repair people. This is our only car. We have been told that the other driver is denying liability so the insurance company won't give a replacement car until this is resolved so we have to rent a car in the mean time. We live in a rural area so my husband has missed 2 days of work so far by not having a car. The insurance company is being extremely unhelpful. Can anyone advise what we can do?