It does look to be an interesting solution, and quite convenient tying together the car and the insurance. However, you'd be surprised what you can achieve on your own just by shopping sensibly. I will probably have to be going through this same issue with my cousin shortly.
Buying the right car is everything...preferably avoid anything popular with the boy racer element (chances are, this will be very unpopular with the youth, who wishes to raise his street cred with a "wicked set of wheels"). Look for simple, safe cars with low powered engines, generally preferred by the "less adventurous" types. If you see an granny driving one to the shops, you're probably on to a winner
Get them to take Pass Plus. Try going on their policy as a second driver, sometimes this can shave a bit more money off.
My other half is only 20, she's had her licence for around 5 months, and requires Business Cat 1 insurance for her job. On a brand new Honda Jazz 1.4, with me as second driver (25, 5 yrs NCB, clean record), we're paying about £500.