Try this - lots of companies do this and you can see the list below
http://www.money.co.uk/car-insurance...-insurance.htm
MULTI-CAR DISCOUNT
An exclusive discount of 10% on additional cars
We don’t want to hit you in the pocket just because you own more than one car. In fact, we are dedicated to doing the exact opposite - saving you money with
our Multi-car Discount.
If you insure additional cars with Direct Line, and you can identify the existing policy in your household or the policy on which you are a named driver, we’ll give you a special 10% discount for your first year and 5% at renewal and every year there after that.
More details on Direct Line
car insurance.