There are companies that promise special deals if you insure two cars but, in my view, that's just a marketing ploy and, if you look at the ads for someone like Swinton, you'll see that they also specialise in insuring women drivers, young drivers, old drivers, van drivers, high-risk drivers, low-risk drivers, etc., etc..
Insurance for young drivers is a silly price in the UK. You will be lucky to get a quote for the sort of money that an average first-time driver could afford which is why there are so many uninsured young drivers on the road. One common ploy is to pretend that a parent is the main driver on both a family car and an old runabout and add the youngster as a named driver on the runabout. Such a policy is not valid if it is obvious that the youngster is the main driver but it would be enough to get a tax disc and avoid most traffic checks. Other youngsters don't get any policy but this is hard to get away with for anything more than occasional use.
There's no real way round shopping around and then paying a silly price to insure a young driver.