Private
Miles per hour. We British have manfully resisted any attempts to 'improve' our systems of measurements as they have on the continent.
There is an unbreakable braking charm, an entirely different sort of sticking charm, flight technique improvements with vectored thrust and reversed control inputs. Even a way to copy goblin-forged irons.
Young sir, we are talking brooms, racing, and Quidditch. I still remember some of the absolutely terrible refugees from the dustbin they wanted the First Years to learn flying on. Even though I will have to teach you some of the underlying magic, I trust a fellow enthusiast such as yourself to use such knowledge in the appropriate manner.