Norwich union do mini-fleet policies (domestic as opposed to commercial) for multiple people and multiple vehicles - we have one - but I would imagine that, for only two cars and two people, it would be uneconomical. You could give them a call anyway. Any halway decent insurance company is going to give you a some sort of discount for taking out a second policy - try calling around the big players and playing them off against each other to get the best discount and overall rate.