Contrary to popular myth, the standard Magnette brakes are very capable of bringing a standard car to a quick unflustered halt. Any reputation to the contrary normally arises from old braking systems in poor condition. Poor braking in an older car is generally caused by worn components, e.g. drums that wear and lose shape compatibility with the shoes. On modern roads, the car is surrounded by others with far superior stopping distances, so it pays to spend some time and money ensuring that your system is at its best. With interchangeability of components with the MGA and other contemporary cars, it is possible to get higher specification linings for fast road or competition work.
If you regularly use your car and cover high mileages at high speed, you may want to consider conversion to disc brakes to improve stopping power. This work is described in a separate article.