When my son turned 17 last year and I got him a Skoda CityGo (75bhp as it was the same insurance price as the 65bhp). I then got him 12 months insurance (on his provision) in his name for about £410 from Adrian Flux, which included an agreement that he would get something back if he passed his test within 9 months.
In November he passed his test, and to upgrade old provision insurance to a full new 12 month insurance was about £1100 (again in his name) which included fitting a data logger in his car (not a black box).
The way the scheme works is they provide his next insurance renewal quote in 12 months (which in his case was £623), however if the data logger detects any poor driving (speeding) then this insurance quote increases each time he is deemed to be reckless. If it detects really poor examples of poor driving 3 times, they reserve the right to terminate the policy.
It's worked very well so far. Plus we both track progress/all of his journeys, etc via an App
The data logger also has a button he can push if he has an accident which will immediately put him through to a 24x7 emergency help line who can talk him through the process.
Highly recommended, plus it has worked so far. He was late for school one morning and drove a bit quicker than he should have - got busted
plus his renewal price only increased by about £2. Since then he has been diving like "Miss daisy". We also banned him for carrying his mates for the first 3 months, plus his car will have P plate until his birthday at the March. I also added a cheap dash cam, just to provide some additional focus".
i must say he is a pretty good and sensible driver, more interested on fuel comsumption than racing around.